feat: inject content script to handle interactions from remote v4 Mastodon instances

[hueyy]

To be merged only after #82 is merged.

Resolves #77

[rugk]

Again thanks a lot and here some mostly code style-related comments.

BTW you marked this as WIP, what is still missing here?

[rugk]

Oh merged, but @hueyy sorry testing it I noticed some bugs/things:

1. It does not work if you open only the toot in a window. See e.g. https://mastodon.social/@drewtoothpaste/109393612157338955
   My first testing shows, this is likely due to the first filtering for the feed/that only considers the feed #mastodon .columns-area__panels__main may be another selector that targets this. Or no, it is somewhere different?
2. When I navigate back from a detailed toot site (via Mastodon's back button or also via the browser's back button) and click an interaction button, it does not work either:
   
   Actually, also when I then click the follow button, it has the same effect?
3. When I click on the interaction button, and the automatic redirection works, and the target instance is a Mastodon v4 instance, it does seem to have problems: It goes to https://chaos.social/authorize_interaction?uri=https://mastodon.social/users/Gargron/statuses/109394489902371854/activity, which looks okay AFAIK, but it only shows me "Could not find remote account."
   Hmm, sometimes the redirection also succeeds, and ends at https://chaos.social/web/@elhotzo@mastodon.social/109395625884664825 e.g., but even then the toot is not shown, but the sidebar shows a 404 error only. I tried this with a toot that provably already exists on my target instance, as such it should be possible to be shown, but it shows only 404.

So unfortunately, I cannot release it as it is.

[hueyy]

@rugk yes, my bad, I accounted for the detailed status page in the inject function but not in the MutationObserver. Will send in a PR to fix this. I think that should resolve (1) and (2).

I can't seem to reproduce (3), even on https://mastodon.social/@drewtoothpaste/109393612157338955. It sounds very odd because yes, the URL looks right.