Enable CWs for given tags when tooting

[hughrun]

Who will benefit from your new feature?

• App users
• App Maintainers / System Administrators
• Developers
• Someone else

Is your feature request related to a problem? Please describe.
Since toots are automated, it's likely that some will include content that would benefit from a content warning.

Describe the solution you'd like
Add a new setting content_warnings that takes an array of strings. These are checked against each post's tags before tooting, and all matching terms are included as a content warning on the toot.

Describe alternatives you've considered
We could simply CW every toot but that seems a bit over the top.

What kind of users will this most benefit?
Mastodon users who don't want to be confronted with upsetting automated toots.

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

[hughrun]

possibly do some kind of regex on the title as well? But maybe then we'd have two problems...