README.md

[Rao-Sanaullah]

Fixes # (no specific issue — community contribution)

Changes proposed in this pull request:

• Added community install guide link to README under a new "Community Guides" section
• Guide covers GR00T N1.7 installation on RTX 5090 (Blackwell / sm_120) for both WSL2 and Docker on Linux
• Includes fixes for Triton sm_120 crash, venv permission errors, Docker volume mount gotcha, and fine-tuning walkthrough

Before submitting

• I've read and followed all steps in the Making a pull request
  section of the CONTRIBUTING docs.
• I've updated or added any relevant docstrings.
• If this PR fixes a bug, I've added a test that will fail without my fix.
  (N/A — documentation only)
• If this PR adds a new feature, I've added tests that sufficiently cover my new functionality.
  (N/A — documentation only)