Improve monthly chores template formatting

I suggest we move additional details for tasks to collapsed sections.

When working through these tasks, I reference the description often, and this will the writers control to have expanded only those sections they're working on.

See how it renders: https://gitlab.com/gitlab-org/technical-writing/-/blob/msj-chores-template/.gitlab/issue_templates/tw-monthly-tasks.md

Related to gitlab!114466 (merged).