Summary:
I had a tough time building this through qmake (its my fault for using NixOS and not adding gstreamer as a dep) but I'll document this for future contributors.

This diff does a few things, split up into individual commits:

1. Adds kirigrami and breeze-icons submodules (for Android)
2. Adds the luv icons submodule and links it to the icons dir
3. Add README with build instructions and troubleshooting

Reviewers: camiloh

Reviewed By: camiloh

Differential Revision: https://phabricator.kde.org/D13855