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
Since all of the details and section classes are going to be under the same basic element block, where should they go in the file the follow common Sass styling? After the ```a{}``` block?