Integrate Community Documentation and Fix Links

[igopalakrishna]

This PR closes #89 by merging the community‑run documentation (https://github.com/gitwyd/sbsim_documentation/) into our official MkDocs site.

Key Changes and Improvements:

• Integration

  • All Markdown pages and assets from the community repo’s docs/ have been moved into docs/community/.
  • mkdocs.yml now includes a top‑level Community Documentation section in the nav, with nested Reinforcement Learning Module pages.

• Link Remediation

  • Converted all Jekyll‑style tags ({% link %}, {{ site.baseurl }}) to standard relative Markdown links.
  • Fixed image paths so all visuals render correctly.

• Cleanup & Consistency

  • Removed the redundant community/contributing.md, keeping only the official guide.
  • Added code-of-conduct.md to the main nav for better discoverability.
  • Updated the root README.md to drop references to the old community site.

• Polish

  • Updated internal fragment links in the dataset module docstrings (./#… to #…) in smart_control/dataset/… to suppress build warnings.

Testing:
Built and served locally with mkdocs serve -- all community pages, links, and assets load without errors.

Closes #89

• Tests pass (N/A for documentation-only changes)
• Documentation updates included