Add new people onboarding page draft

[samumantha]

On Monday we might have a new person joining the team meeting (not just instructor, but team member).
This could be used as "first steps" document?

Please check is something very important is missing :)

[bast]

Thank you!

Something we can add later:

• first steps if you want to join as instructor
• first steps if you want to improve material
• first steps if you want to join a workshop

[samumantha]

closes #244