refactor($compile): simplify regular expressions

Closes #9637
refactor(jqLite): remove a duplicate DOMContentLoaded handler attachment
docs(jqLite): typo: `getComputedStyles()` -> `getComputedStyle()`
docs(ngEventDirs): update remarks on behavior

The event directives haven't stopped propagation by default in a long time.
If that behavior is desired, the handler may use the provided `$event` to call:

    $event.stopPropagation();

Closes #9640
docs(guide/forms): improve readability and formatting