docs(drawer): Add additional documentation for disableClose (#6750)

* create event for ESCAPE keydown

* revert changes and update doc instead

* address comments

* minor modification

* remove mention of drawer

Author: jwshinjwshin

src/lib/sidenav/drawer.ts

@@ -119,7 +119,7 @@ export class MdDrawer implements AfterContentInit, OnDestroy {
   /** Mode of the drawer; one of 'over', 'push' or 'side'. */
   @Input() mode: 'over' | 'push' | 'side' = 'over';
 
-  /** Whether the drawer can be closed with the escape key or not. */
+  /** Whether the drawer can be closed with the escape key or by clicking on the backdrop. */
   @Input()
   get disableClose(): boolean { return this._disableClose; }
   set disableClose(value: boolean) { this._disableClose = coerceBooleanProperty(value); }

src/lib/sidenav/sidenav.md

@@ -70,3 +70,15 @@ html, body, material-app, md-sidenav-container, .my-content {
 ### FABs inside sidenav
 For a sidenav with a FAB (Floating Action Button) or other floating element, the recommended approach is to place the FAB
 outside of the scrollable region and absolutely position it.
+
+
+### Disabling closing of sidenav
+By default, sidenav can be closed either by clicking on the backdrop or by pressing <kbd>ESCAPE</kbd>.
+The `disableClose` attribute can be set on `md-sidenav` to disable automatic closing when the backdrop
+is clicked or <kbd>ESCAPE</kbd> is pressed. To add custom logic on backdrop click, add a `(backdropClick)` listener to
+`md-sidenav-container`. For custom <kbd>ESCAPE</kbd> logic, a standard `(keydown)` listener will suffice.
+```html
+<md-sidenav-container (backdropClick)="customBackdropClickHandler()">
+  <md-sidenav disableClose (keydown)="customKeydownHandler($event)"></md-sidenav>
+</md-sidenav-container>
+```