Draft: new Contributor Program roles to support the Driving Open Source Contribution goal

Why is this change being made?

This is a proposal to constitute a new team to execute the 10x contributor goal as part of GitLab's 3 year strategy on Building on our Open Core strength

Notes:

• Named the Evangelist roles as Contributor Evangelist (Contribution Evangelism) to differentiate them from Developer Evangelists (Product evangelism). This might have an impact in sourcing/attracting candidates, as the contributor part might not be industry standard, so we might want to revisit it.
• Currently the Evangelist roles have a core of responsibilities that are the same, and are effectively duplicated. We might want to list only the core requirements/responsibilities as a single role and add what's specific about each specialty as a separate section. This alternative listing would not change the responsibilities/requirements of the roles.

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)