Add documentation information

[joecummings]

Context

• add a new feature
• fix a bug
• update tests and/or documentation
• other (please add here)

Changelog

• Update CONTRIBUTING.md with instructions on adding documentation
• Change TorchTune -> torchtune in CONTRIBUTING

Test plan

• run pre-commit hooks and linters (make sure you've first installed via pre-commit install)
• add unit tests for any new functionality
• update docstrings for any new or updated methods or classes
• run unit tests via pytest tests
• run recipe tests via pytest tests -m integration_test
• manually run any new or modified recipes with sufficient proof of correctness
  • include relevant commands and any other artifacts in this summary (pastes of loss curves, eval results, etc.)

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/torchtune/896

• 📄 Preview Python docs built from this PR

Note: Links to docs will display an error until the docs builds have been completed.

✅ No Failures

As of commit 562150d with merge base a94803f ():
💚 Looks good so far! There are no failures yet. 💚

This comment was automatically generated by Dr. CI and updates every 15 minutes.

[kartikayk]

Looks great! Thanks @joecummings