docs: add section to ask for feedback

This PR adds a new section to the onboarding course to ask newcomers to request feedback, (partially) addressing #30 (closed).

JIRA tickets: https://tasks.opencraft.com/browse/SE-4442

Discussions: #30 (closed)

Dependencies: None

Screenshots:

Sandbox URL: https://studio.courses.opencraft.com/container/block-v1:OpenCraft+onboarding-dev+course+type@vertical+block@4eda7d513ac4432fb39ba59e3ea0c456

Merge deadline: None

Testing instructions:

1. Open the section
2. Proofread the text
3. Comment any improvement ideas

Author notes and concerns:

This PR will have a pair in the handbook to create a checklist of points to cover during 121s for both the newcomer and its mentor.

Reviewers

• @nizarmah