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
Why are you grabbing all "details.alert"? this initialization is triggered for each details.alert one at a time so there should be no need for a loop. Also elm is already the element you want so if you want a jQuery object just do $( elm ).