Add a section on work/life harmony to the Distribution handbook

Why is this change being made?

Part of updating the Distribution handbook to be better at sharing GitLab's culture and values with new team members.

The idea is that the GitLab handbook itself is too big and daunting to be able to rely on it as an onboarding tool unless we link to SPECIFIC areas.

The goals:

• New team members learn GitLab values and culture from specific GitLab handbook links in their onboarding issue
• The Distribution specific handbook will reinforce those values and culture links, as well as provide 'further reading' areas that branch out into the other areas of the GitLab handbook that we have found to be important/useful to our team.

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
  • Copy/paste the Slack conversation to document it for later, or upload screenshots. Verify that no confidential data is added.
• Assign reviewers for this change to the correct DRI(s)
  • 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.

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