DOC-4604 Move Starlight configuration details to Starlight docs

[aimurphy]

The instructions for configuring the Starlight extensions are split between Astra/Luna Streaming, Streaming Learning, and the Starlight docs repos.
This is one of several PRs that streamline these instructions in one place (each Starlight repo) rather than splitting and duplicating them across 3 repos.

One Starlight overview page remains that introduces the 3 extensions and links to the appropriate docs for each.

• Add Starlight overview page
• Remove the two existing Starlight pages
• Slightly rearrange the Development section of the nav to try to go from basic to complex/optional
• Update links

[plpesvc-ds]

Build successful! ✅
Pull requests with matching branch name doc-4604 included in the build:

• DOC-4604 Move Starlight configuration details to Starlight docs #158 (this pull request)
• DOC-4604 Move Starlight content to Starlight docs repos streaming-learning-docs#68
• DOC-4604 Centralize Starlight for JMS quickstarts from Astra Streaming, Streaming Learning, and Luna Streaming starlight-for-jms-docs#18
• DOC-4604 Quickstart and general cleanup starlight-for-rabbitmq-docs#27

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[mendonk]

+1