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.

🌐 References

Notion project: Algolia search problems

Closed #1052

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