Document alternative way of creating README on Leadership Handbook page

Why is this change being made?

Since 14.5 GitLab has a native support for adding README to GitLab's profile. Many GitLab team members are already actively dogfooding this capability and it seems appropriate to mention this at least as an alternative way of managing your README (we might consider suggesting it as a default way as well?)

Some examples:

• https://gitlab.com/michelletorres
• https://gitlab.com/poffey21
• https://gitlab.com/dzalbo
• https://gitlab.com/kencjohnston

Additional links:

• Issue: User profile customization via README.md in spe... (gitlab-org/gitlab#232157 - closed)
• Docs: https://docs.gitlab.com/ee/user/profile/#add-details-to-your-profile-with-a-readme

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.
• If the changes affect team members, or warrant an announcement in another way, please consider posting an update in #whats-happening-at-gitlab linking to this MR.
  • If this is a change that directly impacts the majority of global team members, it should be a candidate for #company-fyi. Please work with internal communications and check the handbook for examples.

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