Let an Admin post a message to users

[epugh]

Is your feature request related to a problem? Please describe.
Sometimes we need to communicate to users that things are going to happen, and no way to communicate it.

Describe the solution you'd like
Be able to put up a bit o' HTML that is show to the users. Let them click close, and not see it again. If a new message is posted, then they will get the new message. If the message is "timed" well, you remove the message, and then it no longer shows up. It doesn't "expire" by itself.

Describe alternatives you've considered
We have "sort" of used intercom on the hosted solution.

Additional context
Add any other context or screenshots about the feature request here.

[epugh]

This is waht Zoom does.. never thought I would point to Zoom for good UX...

[epugh]

Here is some potential HTML that could go in a messages box...

<div class="alert alert-info" role="alert">
  A simple info alert—check it out!
</div>

[flaxsearch]

Some examples of the sort of messages I'd like to be able to put up (excuse my HTML):

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[epugh]

This has been done for a while!