news: add news for v0.7.1
news: add news for v0.7.1

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