Policy for onboarding new clients and/or new projects

Following the automation issue in #27: We should probably have a guideline / policy in place for onboarding new clients + projects.

This document should be easily accessible. It should be written in a way that makes it able to be communicated externally (clients can see the steps involved in boarding with us and submit all the necessary info early on to move things along). It can start as a draft and mature over time and experience.
It should contain the most basic requirements needed before work on a new projects can begin, i.e. Team Roster set up, team availability checked, proper requirement documentation, contract signed, ...