Fixed typos and grammatical errors in the documentation

* remove some key usage from core, refactor Operations.apply

* undeprecate some methods

* convert more key usage to paths

* update deprecations

* convert selection commands to use all paths

* refactor word boundary selection logic

* convert many at-range commands to use paths

* convert wrapBlock and wrapInline to not use keys

* cleanup

* remove chainability from editor

* simplify commands, queries and middleware

* convert deleteAtRange

* remove key usage from schema, deprecate *ByKey methods

* migrate *ByKey tests, remove index from *ByPath signatures

* rename at-current-range tests

* deprecate mode key usage, migrate more tests away from keys

* deprecate range and point methods which rely on keys to work

* refactor insertBlock, without fixing warnings

* add pathRef/pointRef, fix insertBlock/Inline deprecations, work on insertFragment

* refactor insertFragment

* get rich-text example rendering

* fix lint

* refactor query files, fix more tests

* remove unused queries, refactor others

* deprecate splitDescendantsByPath

* merge master

* add typescript, convert slate, slate-hyperscript, slate-plain-serializer

* add Point, Path, Range, Annotation tests

* add Annotation, Change, Element, Fragment, Mark, Range, Selection, Value interfaces tests

* add Operation and Text tests

* add Node tests

* get operations and normalization tests working for slate

* get *AtPath command tests passing

* rename *AtPath command tests

* rename

* get *AtPoint tests working

* rename

* rename

* add value queries tests

* add element, mark and path queries tests

* convert most on-selection tests

* convert on-selection commands

* rename

* get addMarks and delete commands working

* rename

* rename

* rename

* refactor value.positions(), work on delete tests

* progress on delete tests

* more delete work

* finish delete tests

* start converting to at-based commands

* restructure query tests

* restructure operations tests

* more work converting to multi-purpose commands

* lots of progress on converting to at-based commands

* add unwrapNodes

* remove setValue

* more progress

* refactor node commands to use consistent matching logic

* cleanup, get non-fragment commands passing

* remove annotations and isAtomic

* rename surround/pluck to cover/uncover

* add location concept, change at-path to from-path for iterables

* refactor batches

* add location-based queries

* refactor hanging logic

* more location query work

* renaming

* use getMatch more

* add split to wrap/unwrap

* flip levels/ancestors ordering

* switch splitNodes to use levels

* change split to always:false by default

* fix tests

* add more queries tests

* fixing more delete logic

* add more splitNodes tests

* get rest of delete tests passing

* fix location-based logic in some commands

* cleanup

* get previous packages tests passing again

* add slate-history package

* start slate-schema work

* start of react working

* rendering fixes

* get rich and plain text examples working

* get image example working with hooks and dropping

* refactor onDrop to be internal

* inline more event handlers

* refactor lots of event-related logic

* change rendering to use render props

* delete unused stuff

* cleanup dom utils

* remove unused deps

* remove unnecessary packages, add placeholder

* remove slate-react-placeholder package

* remove unused dep

* remove unnecessary tests, fix readonly example

* convert checklists example

* switch to next from webpack

* get link example working

* convert more examples

* preserve keys, memoized leafs/texts, fix node lookup

* fix to always useLayoutEffect for ordering

* fix annotations to be maps, memoize elements

* remove Change interface

* remove String interface

* rename Node.entries to Node.nodes

* remove unnecessary value queries

* default to selection when iterating, cleanup

* remove unused files

* update scroll into view logic

* fix undoing, remove constructor types

* dont sync selection while composing

* add workflows

* remove unused deps

* convert mentions example

* tweaks

* convert remaining examples

* rename h to jsx, update schema

* fix schema tests

* fix slate-schema logic and tests

* really fix slate-schema and forced-layout example

* get start of insertFragment tests working

* remove Fragment interface

* remove debugger

* get all non-skipped tests passing

* cleanup deps

* run prettier

* configure eslint for typescript

* more eslint fixes...

* more passing

* update some docs

* fix examples

* port windows undo hotkey change

* fix deps, add basic firefox support

* add event overriding, update walkthroughs

* add commands, remove classes, cleanup examples

* cleanup rollup config

* update tests

* rename queries tests

* update other tests

* update walkthroughs

* cleanup interface exports

* cleanup, change mark transforms to require location

* undo mark transform change

* more

* fix tests

* fix example

* update walkthroughs

* update docs

* update docs

* remove annotations

* remove value, move selection and children to editor

* add migrating doc

* fix lint

* fix tests

* fix DOM types aliasing

* add next export

* update deps, fix prod build

* fix prod build

* update scripts

* update docs and changelogs

* update workflow and pull request template

* Removed 404 link of slate-dev-warning

* Removed 404 link of slate-simulator

#### Is this adding or improving a _feature_ or fixing a _bug_?

Debt.

#### What's the new behavior?

This removes almost all existing deprecations from previous API changes, to save on filesize and reduce complexity in the codebase going forward.

It also changes from using the `slate-dev-logger` to using the Facebook-inspired `slate-dev-warning` which can be compiled out of production builds with [`babel-plugin-dev-expression`](https://github.com/4Catalyzer/babel-plugin-dev-expression) to save even further on file size.

The only deprecations it keeps are in the `fromJSON` methods for data model changes like `.kind` and `.leaves` which may still may not have been migrated in databases, since this is a bigger pain point.

#### Have you checked that...?

* [x] The new code matches the existing patterns and styles.
* [x] The tests pass with `yarn test`.
* [x] The linter passes with `yarn lint`. (Fix errors with `yarn prettier`.)
* [x] The relevant examples still work. (Run examples with `yarn watch`.)

#### Does this fix any issues or need any specific reviewers?

Fixes: #1922 
Fixes: #2105
Fixes: #646 
Fixes: #2109
Fixes: #2107 
Fixes: #2018

* Process and Lint CSS, Markdown and JSON files with Prettier

* Run `yarn prettier` to re-format Markdown, CSS and JSON files

* init lerna, move files into ./packages

* move test files into ./packages

* more moving around

* fill out package.json files

* fixing imports

* more fixing of imports, and horribleness

* convert examples, fix linting errors

* add documentation

* update docs

* get tests passing

* update travis.yml

* update travis.yml

* update travis.yml

* update test script

* update travis.yml

* update scripts

* try simplifying travis.yml

* ocd stuff

* remove slate-core-test-helpers package

* add package readmes

* update reference docs structure

* refactor slate-simulator into its own package

* add docs for new packages

* update docs

* separate benchmarks into packages, and refactor them