ipfs-cluster: add some useful configs

[skylenet]

• Allow customizing init scripts via a ConfigMap
• Added extraArgs , extraVolumes, extraVolumeMounts, customCommand to the ipfs container.

[skylenet]

CI is failing with:

INFO: Downloading bootstrap version 'v2.0.0' of cosign to verify version to be installed...
      https://storage.googleapis.com/cosign-releases/v2.0.0/cosign-linux-amd64
ERROR: Unable to validate cosign version: 'v2.0.0'

Should be fixed by updating the action that installs CT. Which uses also another action that installs the cosign tool. That should then use the updated github urls. Fix in here: #249