docs($exceptionHandler): add a note about cases when exceptions are not delegated...

...to the $exceptionHandler

Add a note in $exceptionHandler's documentation about cases when exceptions are not delegated to the
$exceptionHandler, because they are executed outside of the Angular context. Most notable such
cases being the DOM event listeners registered using jqLite's/jQuery's on/bind methods.

Closes #7909
Perhaps add in the detail from @gkalpak that anything executed outside the AJS context will run into this issue...here's my quick edit:

Note, code executed outside of the Angular context, most commonly DOM event listeners (even those registered using jqLite's `on`/`bind` methods), will not delegate exceptions to the {@link ng.$exceptionHandler $exceptionHandler} (unless executed during a digest).