docs: Add RELEASE_PROCESS.md

[gregfurman]

Description

Adds a new RELEASE_PROCESS.md that outlines how we release new SDK and hatchet platform versions.

Type of change

• Documentation change (pure documentation change)

What's Changed

• Included new top-level document that outlines the hatchet release process.

Checklist

Changes have been:

• Tested (unit, integration, or manually with steps specified)
• Linted and formatted
• Documented (where applicable)
• Added to CHANGELOG (where applicable) -- see Keep a Changelog

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🤖 AI Disclosure

• I acknowledge that an LLM was used in the creation of this Pull Request, in accordance with Hatchet's AI_POLICY.md.

• Details: Claude code was used to ensure the full release process was properly reflected in the new doc.

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