Add CI workflow to auto-build and deploy MkDocs documentation to GitHub Pages

[sidhantpande]

Summary

Following the MkDocs setup in #456, we need a GitHub Actions workflow to
automatically build and deploy the documentation to GitHub Pages whenever
changes are merged into main.

What this adds

A .github/workflows/docs.yml workflow that:

• Triggers on every push to main and on pull requests
• Sets up Python 3.10 and uv
• Installs the docs dependency group (mkdocs, mkdocs-material,
  mkdocstrings)
• Builds the docs with mkdocs build --strict (fails on warnings)
• Deploys to GitHub Pages via mkdocs gh-deploy on merges to main

Why This Matters

• Documentation stays always up to date with the codebase
• PRs can verify docs build without errors before merging
• Directly supports GSoC Project Idea Area definition as part of static dataset files #2: Automatic documentation generation
• Related to Structured documentation for Neural-LAM #61

Related

• Structured documentation for Neural-LAM #61 (Structured documentation for Neural-LAM)
• Set up MkDocs documentation system with mkdocstrings #456 (MkDocs setup PR)

[sadamov]

please discuss the CICD aspect of autodocs directly in #230