Added dismissible alert plugin

This is the cleaned up version of https://github.com/wet-boew/wet-boew/pull/5932.
Please note the build will fail because of this issue: https://github.com/wet-boew/wet-boew/issues/5927
Not to avoid Modernizr, just to ensure that the check happens after we are sure Modernizr has executed. Here is a simpler race-safe way of doing this:

Wait until the first timerpoke.wb event. It cannot fire until Modernizr has completed executing. 
```js
$document.one( "timerpoke.wb", function() {
	if ( Modernizr.details ) {
		...
	}
});
```