Review the process for onboarding technical volunteers

[sinke237]

Please leave a review by validating these docs:

Technical Volunteers docs:

Mentors: https://www.notion.so/Onboarding-27a1c4dd7c198083832cf051126fcee0
Trainers: https://www.notion.so/Trainers-27a1c4dd7c198067a2bdc1cfd9006ca0