[discussion] client-contrib plugins release and installation

[zhanggbj]

Opened this item for discussion about client-contrib plugin release and installation

• release

1. Will client-contrib plugins release with kn client or separately?
2. Inside client-contrib release, each plugin will maintain its versions and client-contrib has a list of all versions?

• installation

1. For now, a plugin and be added to kn client like here https://github.com/knative/client/blob/master/docs/README.md#options,
   but usually plugin may have its own repo and end-users can list and install/download a plugin, will client-contribe have something like this?