Create a "playbook" for onboarding new people to BDT

[prestoncabe]

Initial ideas are in this google doc:
https://docs.google.com/document/d/1OqoLhOs45cMGg-V8HbWrFJufI81sCAarMPQlTSrHbE4/edit?usp=sharing

[prestoncabe]

Related: @sierscse 's idea to change how the hack nights are conducted. https://codeforphilly.slack.com/archives/C08MFADDZKM/p1777572435433369