third_party: add third_party.manifest file.
third_party: add third_party.manifest file.

For now this is a simple list of the vendored packages and their versions.

We'll manually update this list to reflect what's in third_party.

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