Media App: Add Navigation Arrows to File Preview Modal

[zcolah]

Is your feature request related to a problem? Please describe. Currently a user cannot quickly navigate between files when in the media app. This can be frustrating when trying to browse through all the files in a folder.

Describe the solution you'd like If a folder has more than 1 item, we should show left and right arrows on either side of the file preview modal that allow a user to quickly navigate to the previous and next file. In addition to this we should allow a user to use the arrow the left and right arrow keys on their keyboard to navigate between these files. See GIF below.

Design Solution in Figma

I have made the Figma design for this here: https://www.figma.com/file/pBgVbMZSItzqRYcEXg2lhe/Media-App?node-id=2326%3A186267

Unfortunately we do not have an icon button for semi transparent dark backgrounds like our backdrop. Hence I have overridden the arrow icon color for the default and hover states.