Adding GitLab Onboarding Feedback page to HB

Why is this change being made?

This MR is creating a separate Handbook page for onboarding experience feedback following a discussion in this issue.

Appreciate any and all feedback on the layout, flow and process @gl-people-exp @emathis @jkalimon

Once we have this merged, we can create an MR to add a task to the onboarding template linking the team member to this page on day 1, and then again under weeks 2-4 asking the team member to create a video for upload.

Author Checklist

• Provided a concise title for the MR
• Added a description to this MR explaining the reasons for the proposed change, per say-why-not-just-what
• Assign this change to the correct DRI
  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to one of the people listed in the "Maintained by" section in on the page being edited.
  • If your manager does not have merge rights, please ask someone to merge it AFTER it has been approved by your manager in #mr-buddies.
  • If the changes relate to any part of the project other than updates to content and/or data files please make sure to ping @gl-static-site-editor in a comment for a review and merge. For example changes to .gitlab-ci.yml, JavaScript/CSS/Ruby code or the layout files. (this requirement has been removed pending identification of a new DRI for the handbook)