Onboarding update

[curtisbarnard]

Proposed changes

• Add a markdown file to the docs folder with the onboarding information to make it more rapidly accessible than going to the google doc at: https://docs.google.com/document/d/1MJMMOdlzyBOVlvKHydSQLTaxcbNqkS1NQufxiJK9jDs/edit#
• Update the broken link on README to point to the new markdown file.

There is a lot of good info in the doc that would be great for first-timers, but also isn't necessary to show on the main README

[curtisbarnard]

Not sure what the failed test is about. I only touched the README and created a new markdown in the docs folder.

[sidetrackedmind]

Thanks for these changes @curtisbarnard. I will approve and we can work on the assignment list at a later date.