add button to remove banner

[Aseem22]

Fixes #3126

Changes: add a button that hides the banner at the top in web editor.

After:

processing_issue.3126.mp4

I have verified that this pull request:

• has no linting errors (npm run lint)
• has no test errors (npm run test)
• is from a uniquely-named feature branch and is up to date with the develop branch.
• is descriptively named and links to an issue number, i.e. Fixes #123

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[raclim]

This looks good to me, thanks for working on this!

I guess one thing to note is that the banner does reappear when you leave the home page (for example, opening your account page or the About modal) which is expected behavior, but might not be clear to a newer user. I don't think this is a major issue though, especially since this banner is temporary and will be taken down by the end of next week.

Thanks again for this, will deploy this soon!