Update TW assigned to dev guidelines

Why is this change being made?

Follows gitlab-org/gitlab!48148 (merged).

The link to dev guidelines no longer says who's the TW assigned to them (https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments-to-development-guidelines). By scanning the page I thought the information wasn't there anymore, and moments later I located it as only "development" on the other projects' table.

The way it is now is hard to find the info, so I added "development guidelines" back to the table as well as explicitly mentioned @marcia and @mjang1 as assigned TWs (as we still have for API guidelines).

I also mentioned that the reviews depend on the complexity of the changes and linked back to where we explain that on the dev docs.

@cnorris does this make sense to you?

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)