Add like/reply/repost-context for Twitter interactions

Although I am trying to move to more IndieWeb-only interactions, I still heavily interact with folks on Twitter.

However, this makes it a bit more difficult for folks reading my social feed, as they end up with no idea what's going on other than "I like this person's tweet".

As part of #347 (closed), I want to support rendering this like/reply/repost-context for any Twitter interactions, so folks reading the feed can see what I'm actually interacting with.

This is added to likes, replies and reposts of Twitter interactions, and is aware of whether the post I'm interacting with is a quote tweet or a reply.

The new context property is expected to a parsed Microformats2 JSON response, such as the expected format from Granary.

Unfortunately we don't always get an alt tag, so we need to put something in to tell screen readers that they're unfortunately not getting anything helpful.

Closes #347 (closed).