kicad: convert fab.mod + add usb micro footprint
Newer versions of KiCAD treat `.mod` footprint libraries as "legacy" and will refuse to edit them. This commit converts the library to the new `.pretty` format. Note that the new format is a folder with loose `.kicad_mod` files, so it needs to be zipped for distribution. Additionally, a footprint was added for the USB micro-B socket that claims to be on inventory.