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
Could this be creating a race condition? Are we certain that Modernizr will complete before this point is reached? It would probably be better to listen for the "wb-ready.wb-details" event on the document node and then attach the additional event handlers if that event is triggered.