Summary:
**Summary**
Updates the changelog and package.json for the v0.11.7 release.

**Test Plan**

`yarn build && yarn test && yarn lint-docs && yarn lint`

`yarn lint-docs` fails like it did on the [v0.11.6 release](https://github.com/facebook/draft-js/pull/2456#issue-427464261).

`yarn lint` fails on not knowing the rule `'fb-www/no-unused-catch-bindings'`, but I'm unsure how to sync it from Facebook internal to Draft.js.

Pull Request resolved: https://github.com/facebook/draft-js/pull/2562

Reviewed By: claudiopro

Differential Revision: D23044013

Pulled By: mrkev

fbshipit-source-id: 40fb92311535f015cd4001c5bf70bbeb54905530