Rename BaseState to WidgetState

This is motivated by a desire to avoid some confusion with a
future patch that adds a RootState struct to unify some of the
other stuff shared between various contexts.

CHANGELOG.md

@@ -70,6 +70,7 @@ This means that druid no longer requires cairo on macOS and uses Core Graphics i
 - `SHOW_WINDOW` and `CLOSE_WINDOW` commands now only use `Target` to determine the affected window. ([#928] by [@finnerale])
 - Replaced `NEW_WINDOW`, `SET_MENU` and `SHOW_CONTEXT_MENU` commands with methods on `EventCtx` and `DelegateCtx`. ([#931] by [@finnerale])
 - Replaced `Command::one_shot` and `::take_object` with a `SingleUse` payload wrapper type. ([#959] by [@finnerale])
+- Renamed `BaseState` to `WidgetState` ([#969] by [@cmyr])
 
 ### Deprecated
 
@@ -215,6 +216,7 @@ This means that druid no longer requires cairo on macOS and uses Core Graphics i
 [#959]: https://github.com/xi-editor/druid/pull/959
 [#961]: https://github.com/xi-editor/druid/pull/961
 [#963]: https://github.com/xi-editor/druid/pull/963
+[#969]: https://github.com/xi-editor/druid/pull/969
 
 ## [0.5.0] - 2020-04-01