[SE-4442] Add 121 checklists for mentors and newcomers
This PR adds a new section to the handbook to help mentors and mentees with 121 checklists, (partially) addressing onboarding-course#30 (closed).
JIRA tickets: https://tasks.opencraft.com/browse/SE-4442
Discussions: onboarding-course#30 (closed)
Dependencies: None
Screenshots:
Sandbox URL: N/A
Merge deadline: None
Testing instructions:
- Proofread the text
- Comment any improvement ideas
Author notes and concerns:
This PR has a pair in the onboarding course repo.
Reviewers
Edited by Nizar