Contrib guide git workflow cycle improvement

[wwarriner]

On the contributor guide: https://docs.rc.uab.edu/contributing/contributor_guide/

Make the git workflow cycle more explicit and step-by-step at a high level.

One-time setup:

1. Fork central repo
2. Clone fork to local development environment (laptop, etc.)

Cycle to start a new feature:

1. Sync fork from central
2. Pull from fork to local
3. Checkout main branch
4. Create and checkout a new branch feat-...
5. Perform development cycle (change, test, commit)
6. Resync (1 & 2 again) and deal with any conflicts
7. Push branch to fork
8. Make pull request from fork to central

Then explain how to do each step in detail in separate sections.