Simplify and improve adding icons to funk

[davidjb99]

As a user, I have one or more icons I want to add to funk. I may have created these myself or have an icon set I want to add from a third party. Presently I have to find an icon pack that has the correct git structure and add this repo to funk. I find the process of adding icons from github to takes me outside my normally workflow and is confusing and buggy (repos are not always added, icons are not always added if structure differs)

@davidjb99 to do a new design

A/C

• User uploads either an individual icon or a folder containing all the icons they want.
• The uploaded icons are visible as 'available icon packs' and can be added to an 'icon set'
• If a user removes an uploaded icon pack the icons added to the 'icon set' remain
• The uploaded icons are cached on our CDN (not in the spec)