Add Single-Person Groups to Categories

This MR adds two of our single-person groups, ML/AI and DevOps for Mobile Apps, to the handbook. This MR includes the directory structure for the Direction pages and outlines the created labels to be used.

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:

• EVP of Product Management - @sfwgitlab
• VP of Product - @adawar
• Product Director Sponsor - @david
• CEO - @sytses

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

• EVP of Engineering @edjdev
• Vice President of Development @clefelhocz1
• Director of Quality @meks
• Vice President of User Experience @clenneville
• Director of Product Design @vkarnes
• The Product Marketing Manager relevant to the stage group(s)