Add "Onboarding Session" to the SOP for New OFOC members

[matentzn]

I have run a basic onboarding covering what the OBO Foundry is about here:

https://docs.google.com/presentation/d/1yMK9i7-qsM3uF2M1fAIbAU6yg3glGk1106BXCV_LXRc/edit

I would like to request this session to be documented as follows:

1. During an OFOC session a volunteer is identified to run the onboarding, typically a member of the Working Group the new member seeks to join
2. During the onboarding session (ca. 60min) OBO Foundry is introduced, the onboarding checklist is reviewed, and the first tasks discussed, if any (see here for the last onboarding we ran).
3. A standard slide deck should be used, and updated, for the overview