• Move Starlight content out of streaming-learning to (primarily) the 3 Starlight docs repos. Luna Streaming (pulsar-docs) and Astra Streaming both have an overview page introducing the 3 extensions.
• Removed the "product" attribute, which isn't useful for this repo and was confusing when moving content to other repos.

Companion PRs:

• Pulsar-docs/Luna Streaming 211x DOC-4604 Starlight content for 2.10_1.x pulsar-docs#173
• Luna 212x DOC-4604 Starlight content for 2.10_2.x pulsar-docs#174
• Luna 213x DOC-4604 Starlight content for 2.10_3.x pulsar-docs#175
• Luna 313x DOC-4604 Starlight content for 3.1_3.x pulsar-docs#176
• Astra streaming DOC-4604 Move Starlight configuration details to Starlight docs astra-streaming-docs#158
• Starlight JMS DOC-4604 Centralize Starlight for JMS quickstarts from Astra Streaming, Streaming Learning, and Luna Streaming starlight-for-jms-docs#18
• Starlight Kafka 1 DOC-4604 Unified Starlight for Kafka quickstart and style cleanup (2.10.0.x) starlight-for-kafka-docs#25
• Starlight Kafka 2 DOC-4604 Unified Starlight for Kafka quickstart and style cleanup (2.10.1.x) starlight-for-kafka-docs#26
• Starlight Rabbit 1 DOC-4604 Starlight quickstart and general cleanup for v 2.10.0.x starlight-for-rabbitmq-docs#26
• Starlight Rabbit 2 DOC-4604 Quickstart and general cleanup starlight-for-rabbitmq-docs#27
• Redirects https://github.com/riptano/docs-infra/pull/191