feat(realy): Add Relay best practices guide

[Dav1dde]

Closes: https://github.com/getsentry/team-ingest/issues/90

Some best practices for development on Relay.

IS YOUR CHANGE URGENT?

Help us prioritize incoming PRs by letting us know when the change needs to go live.

• Urgent deadline (GA date, etc.):
• Other deadline:
• None: Not urgent, can wait up to 1 week+

SLA

• Teamwork makes the dream work, so please add a reviewer to your PRs.
• Please give the docs team up to 1 week to review your PR unless you've added an urgent due date to it.
  Thanks in advance for your help!

PRE-MERGE CHECKLIST

Make sure you've checked the following before merging your changes:

• Checked Vercel preview for correctness, including links
• PR was reviewed and approved by any necessary SMEs (subject matter experts)
• PR was reviewed and approved by a member of the Sentry docs team

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Name	Status	Preview	Comments	Updated (UTC)
develop-docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Nov 22, 2024 11:52am

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