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
Probably best to just throw it in a try/catch block to catch the privacy mode of some browsers: https://github.com/wet-boew/wet-boew/blob/master/src/plugins/tabs/tabs.js#L95-L114. I don't think your check would catch that scenario as the object does exist, it just rejects writes and reads.