Interactive/Live Filters

[jobobby04]

Depends on #50

There are some sites that change the filters based on the listing and the current state of other filters. One example would be ArchiveOfOurOwn.org. When you continue to set specific filters it will trim available filters with the available work's tags. So if there are more Female Protagonist works it will show the Female Protagonist tag unless there are more of other tags.

My proposal:
Allow an extension to return a new/modified filter list when filters are applied, and allow the extension to modify the states of those filters. On ArchiveOfOurOwn.org you can exclude a tag and it will stay in the filter list, but it will be moved to the bottom. Returning a new filter list with these states set will allow the extension to make these changes.

This also requires that the filter list has loading states where some options are only possible at certain times, so the filter list would need to load filters from the network in the background.