Studio support for creating and editing libraries (PR 6046)

Duplicates https://github.com/edx/edx-platform/pull/6046 to allow Marco to review without spamming the reviewers on the original PR.
I will make final edits to the template in a separate doc PR, but for now please remove "Help text here" just in case.
Suggested for now: "Add and edit components that you want to use in multiple courses. Scroll to the bottom of the page to add a new component to your library."