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
You should avoid using jQuery where possible to help performance. In this case, this.id would work fine (or elm.id one the loop is removed).