Add an option to always expand Mastodon posts marked with content warnings

[Jackenmen]

I think that there should be an option that would cause posts with content warnings to be always expanded. There appears to be a "Display sensitive content" option already but it doesn't affect posts with content warnings.

See #1465 for background on why the lack of such a feature makes it incredibly hard to browse posts with content warnings as Mastodon propagates the content warnings to all follow-ups and replies by default.