Docs tab in CollectionSettings is clunky/not super pretty

[lizziemac]

• When the documentation is very long, the height of the markdown UI is very long, and hid the collection tabs on scroll
• Clicking away saves your progress, but it doesn't feel obvious
• There's no placeholder text
• Double clicking takes you into edit mode, which is a little annoying if you're just trying to copy/paste from the docs
• The button is underwhelming, located awkwardly