feat(admin): easily pin content types and control what's pinned

[mikulthegreat]

Problem

For non-technical users, it's hard to define a new content type, then create content.

Proposal

There should be an option in the features when defining a new content type to "appear in content"
I think ultimately it would be nice to adjust the content sort order here so I can control where it appears, but I think if this was just a boolean to appear or not, and I could adjust it elsewhere (maybe dragging and dropping in the left hand sidebar) that would work as well.

Context
I just created "About" and I want to be able to create new "About" content, but can't figure out where to go. I should be able to easily control what appears on the content sidebar without having to write code. New content types shouldn't just appear here by default or the area will get to be unusable.