* fold Stack into Editor
* switch Change objects to be tied to editors, not values
* introduce controller
* add the "commands" concept
* convert history into commands on `value.data`
* add the ability to not normalize on editor creation/setting
* convert schema to a mutable constructor
* add editor.command method
* convert plugin handlers to receive `next`
* switch commands to use the onCommand middleware
* add queries support, convert schema to queries
* split out browser plugin
* remove noop util
* fixes
* fixes
* start fixing tests, refactor hyperscript to be more literal
* fix slate-html-serializer tests
* fix schema tests with hyperscript
* fix text model tests with hyperscript
* fix more tests
* get all tests passing
* fix lint
* undo decorations example update
* update examples
* small changes to the api to make it nicer
* update docs
* update commands/queries plugin logic
* change normalizeNode and validateNode to be middleware
* fix decoration removal
* rename commands tests
* add useful errors to existing APIs
* update changelogs
* cleanup
* fixes
* update docs
* add editor docs
#### Is this adding or improving a _feature_ or fixing a _bug_?
Debt.
#### What's the new behavior?
`createHyperscript` takes an options object that now looks for the `decorations` property instead of the `decorators` property
#### How does this change work?
Pretty straightforward rename of an option, then all of its uses and wherever the term decorators showed up in docs
#### 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: #1996
Reviewers: @ianstormtaylor
