Add Public Sector Services group

Adds the US Public Sector Services group, which is working on a SaaS service for the US public sector.

Approvals

Merge requests with changes to stages and groups and significant changes to categories need to be created, approved, and/or merged by each of the below:

• VP of Product @david
• The Product Director relevant to the affected Section(s) @joshlambert
• The Engineering Director relevant to the affected Section(s) @marin
• Director of Product Design @vkarnes

The following people need to be on the merge request so they stay informed:

• Chief Technology Officer @edjdev
• Vice President of Development @clefelhocz1
• Vice President of Quality @meks
• Vice President of User Experience @clenneville
• The Product Marketing Manager relevant to the stage group(s)
• Director of Technical Writing @susantacker

After Approvals and Merge

• Create an issue in the triage-ops project to update GitLab Bot automation
  • gitlab-org/quality/triage-ops#1071 (closed)
• Mention the product group Technical Writer to update the documentation metadata
  • Seems not applicable since there is no existing documentation for the group to take over.
• Share MR in #product, #development, and relevant #s_, #g_, and #f_ slack channels