docs(changelog): add missing breaking changes (#7585)

Author: jelbourn

CHANGELOG.md

@@ -18,6 +18,10 @@
 
 ### Breaking Changes
 
+* All "md" prefixes have been removed. See the [deprecation notice in the beta.11 notes for more
+information](https://github.com/angular/material2/blob/master/CHANGELOG.md#deprecation-of-md-prefix).
+* All cdk re-exports in `@angular/material` have been removed. See the [the beta.10 notes for more
+information](https://github.com/angular/material2/blob/master/CHANGELOG.md#breaking-changes-2).
 * Previously the `ScrollDispatcher.scrolled` subscription would react both on scroll events and on window resize events. Now it only reacts to scroll events. To react to resize events, subscribe to the `ViewportRuler.change()` stream.
 * `UniqueSelectionDispatcher`, `UniqueSelectionDispatcherListener` and `UNIQUE_SELECTION_DISPATCHER_PROVIDER` are no longer
 available from @angular/material and instead must be imported from @angular/cdk/collections

guides/theming.md

@@ -172,7 +172,7 @@ an additional step is required for those components to be affected by the theme'
 To do this, you can add the appropriate class to the global overlay container. For the example above,
 this would look like:
 ```ts
-import {OverlayContainer} from '@angular/material';
+import {OverlayContainer} from '@angular/cdk/overlay';
 
 @NgModule({
   // ...