Banner for Superset upgrade

[heisenberg1205]

Make sure these boxes are checked before submitting your issue - thank you!

• [] I have checked the superset logs for python stacktraces and included it here as text if there are any.
• [] I have reproduced the issue with at least the latest released version of superset.
• [] I have checked the issue tracker for the same issue and I haven't found one similar.

Superset version

.27

Expected results

Is there a possible way to put the banner on existing Superset in bright color with the text "we're upgrading Superset for better experience. Please click here" ?

Actual results

Steps to reproduce

[stale]

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[MM-Lehmann]

Would like to reopen this.
A markdown banner like in gitlab would perfectly fit our needs to inform users of upcoming maintenance and downtimes.
Any chance to do this in javascript? (I've played around a little in the past but couldn't get anywhere near that)

[toransahu]

+1 to this feature request. We also need this.