create a Firefox™ manifest (fixes #42)
create a Firefox™ manifest (fixes #42)

potch/moz-games,deathping1994/moz-games,chirilo/moz-games,deathping1994/moz-games,mozilla/moz-gdc,chirilo/moz-games,potch/moz-games,mozilla/moz-games,mozilla/moz-gdc,mozilla/moz-games