Fix search indexing for html commands and changelog

[sfc-gh-dmatthews]

📚 Context

Streamlit commands ending in .html were not indexed correctly (#1052). Additionally, the changelog was not getting indexed because it was too long. This PR fixes that.

🧠 Description of Changes

• The search index build script uses match with a regex expression instead of split(".html") which resulted in incorrect results for pages ending in "...html.html".
• The changelog has been broken apart. The main changelog page only contains those versions which we still document. The rest are moved to an archival page which isn't indexed by Algolia, but is linked from the main changelog.
• Color was added to the search index build script so search results can be color coded to match their categories.

🌐 References

Notion project: Algolia search problems

Closed #1052

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[sfc-gh-dmatthews]

@sfc-gh-tteixeira I went into the search index and manually added a color for the "Quick reference" page. It won't change how the production site displays anything since it's unused, but it let's you see a hypothetical category color incorporated in this preview:

From pattern-matching (since I'm not sure the best way to test-run the script), I'm guessing we can pull the colors in the same way we pull the icons. In this way, search results can be color-coded to match their categories. There are two different CSS files for the search modal, so the highlight color is suboptimal as it is less direct (using an <em> child of a classed container rather than the direct highlight class applied to <em>). I wasn't quite sure if there was a good way to mix classes between to the files... What I really want is something like .IndigoHighlight ais-Snippet-highlighted, but I don't know if there's a trick to do that.