Update team list w/ @mjang1's doc responsibilities

Why is this change being made?

Add a list of Mike Jang (@mjang1's ) doc responsibilities per https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers

Intent: help GitLabbers who ask "whose responsible for this doc"

Does this MR meet the acceptance criteria?

Assign to DRI

• Did you assign this change to the correct DRI of the page or information you are changing?

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what