Integrate wiki-link plugin

[tukib]

This PR:

• implements a wrapper for the @docusaurus/plugin-content-docs plugin
• integrates the remark-wiki-link plugin into Docusaurus, which fixes Port and update Wikilink Docusaurus plugin #32
• adds some associated styling
• adds unlisted¹ page to demo some of this: Wiki-Link Demo (not live so replace the hostname)
• adds another unlisted page that broken/new wiki links point to, which we should fill out at a later stage: Create a Page

I've used TypeScript for this, which builds fine with our current configuration, and can of course be switched to JS if needed.

Some items not in scope for this PR:

• VSCode is giving me a warning for wikilinks (link.no-such-reference)
• Spaces are not replaced when checking/generating slugs in the page name resolver, we need a policy for filenames. (affects line 52, slugReference)
  • Assuming snake-case for doc (mdx) files, we should include some policy in the content guide.
• Would be nice for the 404 page to include a link to create the page on github. addressed already
• The page resolver already knows if a page does not exist, so the permalinks list is redundant, but changing this is probably not trivial.

Footnotes

1. Unlisted pages https://docusaurus.io/blog/releases/3.0#unlisted-content ↩

[danswann]

We can fix the build failure caused by the broken link check by using options.hrefTemplate in the remark-wiki-link plugin.

If you return an empty array from options.pageResolver when there is no valid document, you can check for that in options.hrefTemplate and set a default path. See the prototype wiki configuration for an example.

This also allows us to explicitly set it up so that broken wiki links will link to a page describing how to add a new page, without requiring us to interfere with the default 404 behavior, which we may want to preserve. You can see it in action in the first two links present on the prototype wiki.

[danswann]

This also does not have feature parity with the prototype version. This is probably my fault, as while I named the issue "port and..." I failed to specify in the issue body what porting meant and that an existing working version even existed.

I'd like to see support for an array of custom link text (e.g. we might want [[robovac_catesby]] and [[catesby]] to both correctly resolve to a page with a slug of /foo/bar/robovac_catesby). There's also an argument that this would be redundant with remark-wiki-link's support for aliases, so maybe this is just me. I'm happy to consider this out of scope if we want, since it wasn't clear from the issue description.

Other than that one thing, this is a significantly better version than the one I made. The wrapper is very clean, and my fears of harming maintainability are assuaged. Nice work.

[danswann]

Requested changes made, default page feature added, looks good.