Update "getting started" doc to discuss how to contribute

[kcooney]

We should have a section of the doc focused on the 2024 robot that discusses:

• how to get access to github
• how to clone the repo
• how to build the code
• how to run the tests
• how to create a pull request associated with an issue

[cuttestkittensrule]

I am currently working on a guide to command-line git, which will help people get started with git