Add fp-info-cache to KiCad gitignore (#3013)

See https://lists.launchpad.net/kicad-developers/msg38339.html and https://lists.launchpad.net/kicad-developers/msg38638.html

KiCad.gitignore

@@ -12,6 +12,7 @@ _autosave-*
 *-rescue.lib
 *-save.pro
 *-save.kicad_pcb
+fp-info-cache
 
 # Footprint cache
 fp-info-cache