Add TST integration

[bovine3dom]

Replacement for #1260. Will close #377 once merged.

Edit: this page is useful for reference https://github.com/piroor/treestyletab/wiki/API-for-other-addons#register-and-unregister-your-addon-to-tst

[bovine3dom]

Given that I don't use TST, and that I'm not really sure what people expect out of its integration, I'm going to abandon this PR in the hope that someone with more enthusiasm picks it up - #377 is one of our most requested features, so it would make you lots of friends :)

Happy as always to assist with questions either here or on Riot.

[bovine3dom]

From @saulrh in #1664:

Provides: the low-hanging fruit. tabprev/tabnext only move to visible tabs. tstup moves to ancestors of the current tab. tstcollapse and tstexpand to toggle visibility.

Infrastructural work: Make lib/extension_info.ts more ergonomic and add some features. Fix some bugs in the TST registration code e.g. not specifying listeningTypes and not trying to use nonexistent localizations. Use the extension_info lib to make the code cleaner and safer. Add some super-bare-bones types for TST's tabs and enums.

Remaining: tree information in completions, tree navigation in completions, actual thought put into the excmds for navigating around the tree because the stuff I have now would be super hard to bind usefully and is mostly a POC.

The tests pass, but I didn't do a ton of testing with TST disabled, so run this for a bit on your non-TST-enabled browsers to makes sure I didn't cause any breakage elsewhere.

[bovine3dom]

Todo:

• Give better errors when TST is not installed

[bovine3dom]

Someone mentioned that :winmerge (#404) doesn't preserve the tree structure of tabs - perhaps this is something that the integration could do. tab{grab,push} should probably gain an option to also push/grab the descendants of a tab.

[bovine3dom]

Closing in favour of #2569