[Design] Consolidate figma files for custom media preview

[setch-l]

The nos app presently uses the native ios link preview to display all media. This means it includes links to the cdn where the media is stored, plus weird bars when the media has not yet loaded.

Acceptance criteria

• create a new page in figma titled Custom media preview
• Move all the existing files for custom media preview display including
• • images
• • external links
• • Videos
• • music files