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.