Contextual page/note URLs only embeddable with shortcodes

[Justin Reese]

Pages/notes can only be embedded with a shortcode or with their canonical URLs:

Check this out:

https://www.documentcloud.org/documents/282753-lefler-thesis/pages/57.html

Since canonical URLs aren't surfaced, we need to also support single-line embedding with contextual URLs:

Check this out:

https://www.documentcloud.org/documents/282753-lefler-thesis.html#document/p57

[Justin Reese]

58eb44b