docs: add docs from docs repo to product repo, add gh-action to sync repos

[Anmol1696]

No description provided.

[Copilot]

Pull Request Overview

Adds documentation from the external docs repository into the product repo and introduces a GitHub Action to keep both in sync.

• Adds new “Developing” guide under docs/developing/, including AST usage details
• Registers menu entries via _meta.json files for root and “developing” sections
• Implements .github/workflows/docs.yaml to clone, sync, build, and push docs to the external repo

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
docs/developing/index.mdx	New high-level developer guide with setup, build, and test
docs/developing/ast.mdx	Detailed AST fixture editing and generator instructions
docs/developing/_meta.json	Adds sidebar entries for “Developing” pages
docs/_meta.json	Adds root sidebar entries for docs sections
.github/workflows/docs.yaml	Workflow to sync, build, and commit changes to external repo