feat: add check citations command to see unused cites

[buehler]

Hi there :-)

I really like using your extension and thought to add a new command
for BibTeX files. It would be very cool to have this inserted into the
workshop extension.

This PR adds a new command to the action-bar under the bibtex
category. It allows people to use the "checkcites" command line tool
that is shipped with recent Tex installations. The user then sees
a list of unused citations and can directly jump to them.

As such, you can cleanup your citations at the end of your paper.

I know that I still need to provide translations. Do I need to do them for all
languages? Because I'll not be able to do that.

I'll open this PR as a draft until I know how to proceed.

[James-Yu]

Thank you for your contribution. If I understand correctly, this feature is somewhat of the same kind with lw.extra.counter right? These features should reside in src/extra and have minimal code injections in other source files, in order to be maintainable.

I agree that files in extra/ are not quite minimally intrusive at their current state. However, new standalone features need to be as "sneaky" as possible.

[buehler]

fair enough :) I'll rearrange stuff according to your guidelines

[buehler]

Is it ok, if the command stays inside the bibtex section in the action bar? It is related to bibliography and as such it makes sense to keep it there.

I change the files to be in extra.

[James-Yu]

Thanks for the changes. There is one minor thing before the next step: there are unnecessary changes in linter.ts. Please revert.

In the meantime, I am still considering how to better arrange the extra/ features. It is more an architectural design, and any final thought won't require you to make additional changes. Just maybe some more time before I confirm my thoughts and merge.

[buehler]

I just checked, linter.ts has no changes in it (according to the changed files tab)

[buehler]

ah, I get it, you mean src/lint/index.ts

[buehler]

Reverted the changes.