DevRel: Documenting Onboarding Process

[shreythecray]

Please

• [x] Add all onboarding templates in onboarding repo
• [x] Document process for new sourcers to take over

[kavuong]

FYI @shreyagupta98, Collin (@nilloc400) will finish this by Tuesday. Issue is here: https://github.com/bitprj/bitproject/issues/106