docs(codeowners): add amelia as pajamas maintainer

After nearly a year of working on my trainee maintainer issue 😅, @rayana suggested I start a MR to make it all official.

She suggested I highlight both maintainer-level reviews and areas to continue working on for y'all to review.

Larger efforts

• Organizing the Pajamas contribution survey to better understand the team's pain points for contributing to Pajamas.
• Creating the Pajamas maintainer checklist
• Re-working the content on the charts page

Maintainer-level reviews

• gitlab-com/www-gitlab-com#6394 (comment 525558560)
• gitlab-com/www-gitlab-com#6394 (comment 584373616)
• gitlab-com/www-gitlab-com#6394 (comment 548643129)
• gitlab-com/www-gitlab-com#6394 (comment 541408483)
• gitlab-com/www-gitlab-com#6394 (comment 526596544)
• gitlab-com/www-gitlab-com#6394 (comment 584382270)
• gitlab-com/www-gitlab-com#6394 (comment 525558579)

(Full list of reviews on my trainee maintainer issue)

Things I want to continue working on

• Looking at things with fresh eyes to make sure I haven't missed anything (to catch all the small details that might otherwise slip through the cracks).
• Continuing to improve my skills in terms of rebasing and squashing commits.
• Still also working on assessing the status table to ensure it's accurate. Noting that's still very much WIP!

Depending on discussion on this MR, I will update my handbook details accordingly.