docs: update roadmap
docs: update roadmap

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