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
or you could just manually do

```js
try {
  doAThingThatMightThrow();
} catch (e) {
  $exceptionHandler(e);
}
```

This is a pretty detailed and long-winded explanation, I think we can condense this down a bit so that it's easier for people to read. SGTY?