as a user, I can use repo content in posts/comments

I have a way to use filenames as part of the post. The filename in the post is a link to the content in the repo.

as seen in this prototype:
https://projects.invisionapp.com/share/D4NXUZFMXBH#/screens/317357794

we click the link icon, and we "browse" through the content to select the objects to include as the link.
we can choose multiple items (in a single browse, if possible, if not, one by one) and can remove the link if we'd like (via an action in the link listing, an x)