feat: add graph search to check for broken links

[nickwynja]

This feature runs a link search against all files in the wiki and opens a loclist with any wiki links that point to non-existing files. It's good to check for broken links after a migration or to check if any red links need to be updated.

[lervag]

Nice! I was just about to shut down and go to bed, so I'll review tomorrow. But I have actually been planning this feature for a long time, but never got around to it. Thanks!

[lervag]

Thanks! I've made some minor adjustments, but this was a very high quality contribution! Much appreciated!

[lervag]

Also, perhaps it should be added to the docs that this command can be slow? In my wiki of ~4500 files and 209000 lines of text, it took perhaps 45 seconds.

[nickwynja]

Thanks! The code base is set up nicely so that helped with getting a good PR in. I'm happy to add some documentation about the slow processing. I was also starting to look at adding caching like the backlinks graph but that seemed a bit overcomplicated since this likely wouldn't be as frequent of a command as checking backlinks.

[lervag]

Yes, great, that would be appreciated. I don't think it is necessary to optimize this part, really; I would say it is something one should not need to run often, and it is not a large drawback that it can be somewhat slow. Most people probably has a much smaller set of files than myself, so it should be faster. I guess.

I've already used this now to fix ~800 broken links :)