Add docs CI, API reference generator, and Read the Docs integration

[Gonza10V]

Motivation

• Provide automated documentation generation and ensure the API reference stays current by adding a CI job and a generator script.

Description

• Add a GitHub Actions workflow ./github/workflows/docs.yml that installs dependencies, runs python tools/update_api_reference.py, builds the Sphinx site with sphinx-build -b html -W --keep-going docs docs/_build/html, and commits any regenerated docs/API_Reference.rst back to the repo.
• Add tools/update_api_reference.py which discovers modules under src/buildcompiler, organizes them into ordered sections, and renders docs/API_Reference.rst with .. automodule:: entries and Sphinx directives.
• Commit a generated docs/API_Reference.rst containing the current API layout produced by the generator.
• Update README.md to include a Read the Docs badge and a short note linking to the documentation hosted at buildcompiler.readthedocs.io.

Testing

• No automated tests were executed as part of this PR; the new CI workflow will run on pushes to main and build the documentation using the sphinx-build command specified in ./github/workflows/docs.yml.

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Codex Task