feat(tabs): pass the selected tab index to onDeselect

-  Add the index of the tab the user attempted to open to the onDeselect call, which allows the user to directed to the selected tab
after some work is performed.

- Closes #5820

src/tabs/docs/readme.md

@@ -33,7 +33,7 @@ AngularJS version of the tabs directive.
 
 * `deselect()`
   <small class="badge">$</small> -
-  An optional expression called when tab is deactivated. Supports $event and selectedTabIndex in template for expression. You may call `$event.preventDefault()` in this event handler to prevent a tab change from occurring. The selectedTabIndex can be used to determine which tab was attempted to be opened.
+  An optional expression called when tab is deactivated. Supports `$event` and `selectedTabIndex` in template for expression. You may call `$event.preventDefault()` in this event handler to prevent a tab change from occurring. The `selectedTabIndex` can be used to determine which tab was attempted to be opened.
 
 * `disable`
   <small class="badge">$</small>