docs: add ec2 to supported platforms
docs: add ec2 to supported platforms

higebu/ignition,AlexNPavel/ignition,trnubo/ignition,ajeddeloh/ignition,dgonyeo/ignition,coreos/ignition,higebu/ignition,dgonyeo/ignition,coreos/ignition,marineam/ignition,AlexNPavel/ignition,coreos/ignition,jonboulle/ignition,higebu/ignition,ajeddeloh/ignition,trnubo/ignition,trnubo/ignition,dgonyeo/ignition,jonboulle/ignition,AlexNPavel/ignition,marineam/ignition,marineam/ignition,jonboulle/ignition,ajeddeloh/ignition