Index configuration properties and provide a dedicated search endpoint (and webapp?)

[yrodiere]

The full list of (core) configuration properties on the Quarkus website is huge. Search is also implemented in Javascript, and performance has become quite bad -- at least in my case, testing with Firefox.

We should consider having a dedicated index for configuration properties on search.quarkus.io, so that this page's search feature could be offloaded to search.quarkus.io, similarly to what we did for https://quarkus.io/guides

How to perform indexing exactly is TBD:

• We could scrape the full HTML page, though that would be potentially fragile and prevent us from collecting interesting metadata (e.g. source extension).
• We could use extension metadata directly, though it would be more complex to retrieve (where is that metadata?) and may involve Asciidoc rendering.
• ... something else?

cc @gsmet: your overhaul of config annotation processing and metadata (quarkusio/quarkus#42141) will most likely have an impact here.

[yrodiere]

• We could scrape the full HTML page, though that would be potentially fragile and prevent us from collecting interesting metadata (e.g. source extension).

quarkusio/quarkusio.github.io#1796 tells us that this full HTML page is becoming too large, to the point of loading being problematic in some (most?) browsers.
So we probably won't do this. Actually, once we have functional search, we most likely won't include any hardcoded properties on this full HTML page, and will only display results returned by search.quarkus.io.

• We could use extension metadata directly, though it would be more complex to retrieve (where is that metadata?) and may involve Asciidoc rendering.

Looks like we're going that route.