Add some proper tooling to the codebase

[Nuclear-Squid]

Being knee deep in the refactor for the analyzer (see #243), I’m realizing that the code base is starting to get too complex for us to keep doing stuff by hand, a bit of CI would be good.

I’m thinking we should get the triple combo of LSP / linter + auto-fomatter + unit tests, along with some type checking. We discussed the last subject with @fabi1cazenave IRL, but JSDoc could be a good start, as Typscript would add a bit too much complexity, mainly for our sister projects (mainly Kalamine).

Unit tests can be hard to implement before (#243) is merged, but the other three could be added in the mean time. I was thinking we could use eslint + prettier for JS and markdown-lint for the content of the site. Prettier is technically already in use in the code base, but it’s not linked to any kind of CI, so it was used once and never again (and that was a long time ago, before we switched over to Hugo).

I’m assigning you, @fabi1cazenave for this issue, but it’s mainly because you know this ecosystem a lot better than I do. I’ll gladly add those in if you don’t have much time.