* Update type definitions and docs for legends
* Fix types for onHover and onClick callbacks
core.controller.js's implementation also passes the Chart instance as `this`. However, that isn't documented, and it's my impression that Chart.js is moving away from passing items as `this`, so I didn't declare it in the type definitions.
* Allow multi-line ticks
* Stricter DeepPartial definition
The previous definition resolved to `{}` (which can allow primitives) if it was given a function, so it was far too broad for any `Scriptable<>` properties.
* Grammar and writing style
* Updates to animation docs
Document the `fn` option, since it's in the type definitions.
Fix callback usage to match example code.
* Fix AnimationEvent parameter
The onProgress and onComplete events were mistakenly declared as taking the standard DOM AnimationEvent. (Should Chart.js's AnimationEvent be renamed to ChartAnimationEvent to avoid any possible ambiguity?)
* Allow false for disabling animations
* Add comments explaining the layout and usage of Rollup
