Add sections to a document

[eyeseast]

Sections are pretty simple: https://www.documentcloud.org/help/api#sections

This can probably happen in the annotation view, or maybe in the sidebar.

[eyeseast]

Was on NYT Cooking and really like this interface for adding a folder to my recipe box:

Adding sections might be pretty close to that. I'm thinking this lives entirely in the sidebar.

[allanlasser]

Two mockups to share here:

1. Update page header with page actions Figma

2. Section Form Figma