Update Developer Relations handbook: Consistent name, OKRs, workflows (Common Room), formatting, etc.

Why is this change being made?

💡 Provide a detailed answer to the question on why this change is being proposed, in accordance with our value of Transparency.

This MR review is part of the Fix Fridays content review in https://gitlab.com/gitlab-com/marketing/developer-relations/dev-evangelism/de-tmm-meta/-/issues/341

The Developer Relations landing page in the handbook had outdated information, and required changes for consistency, too.

1. Use consistent naming of Developer Relations and developer-relations
   1. Includes URL checking for HTTP 200, and redirect updates.
2. Update the OKR process with new URLs and instructions.
3. Update the team touchpoints to be consistent.
   1. Add end of week updates document and how to find it.
4. Add workflows: Common Room, Discord
5. Formatting and grouping of team handbooks and sections
   1. Change long list of workflows into actionable buttons with font-awesome icons
6. Remove the group conversation section -- this team task was deprecated in FY23.

Author and Reviewer Checklist

Please verify the check list and ensure to tick them off before the MR is merged.

• Provided a concise title for this Merge Request (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, and the content is SAFE
• Assign reviewers for this MR to the correct Directly Responsible Individual/s (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 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
  • The when to get approval handbook section explains the workflow in more detail
• For transparency, share this MR with the audience that will be impacted.
  • Team: For changes that affect your direct team, share in your group Slack channel
  • Department: If the update affects your department, share the MR in your department Slack channel
  • Company: If the update affects all (or the majority of) GitLab team members, post an update in #whats-happening-at-gitlab linking to this MR
    • For high-priority company-wide announcements work with the internal communications team to post the update in #company-fyi and align on a plan to circulate in additional channels like the "While You Were Iterating" Newsletter

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