Filter out content in rss and video feeds

### Description

It would be great to filter out rss and video content that contains a set of user configurable keywords. Even on a standard rss feed, there will be topics you just want to not have to think about.

It could be configured through entering a comma delimited list of words or phrases that would prevent display of the story (or video). Ability to build a regular expression would give the same capability and even more freedom, but regex isn't for everyone.

I don't see a downside and all upside to this feature. We already curate our list of rss feeds/videos to our interests. This lets us curate one further level to the content in the feed.

The issue does not name any files, tests, or entry points. Trace how RSS and video content is configured and rendered, then define how comma-delimited keywords should be stored and applied; done means matching stories and videos are omitted from their feeds.

Written by the indexing model from the issue text.