added data api guide (hackathon submission)

[devagrawal09]

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• [ ] This PR references an issue (except for typos, broken links, or other minor problems)

Description

Added a new section to SolidStart Learn docs called Guides Added a guide to SolidStart Learn docs for using data API. This guide covers This guide might have some redundant information from the data loading docs as well as the reference docs on the solid-router data APIs. I tried my best to keep the guide succinct and link the reference docs wherever applicable for more info. Long term it's gonna take a while to find the best balance of tutorial, guide, and reference content in these docs. This guide also doesn't really cover client side usage, so we would likely need another guide that lives in the router docs for purely client side usage.

This guide anticipates this PR and uses query instead of cache, and mentions the action onComplete hook for advanced cache management.

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