Convert the Argo Rollouts CLI to standalone executable

[kostis-codefresh]

Currently the Argo Rollouts CLI is documented to be a kubectl plugin. However I have successfully used the CLI on its own for most needed actions (watching a rollout, promoting a canary etc) without the need of kubectl.

Unless I am missing something the Argo Rollouts CLI is self-contained.

Would it make sense for consistency reasons to just document it as a standalone executable? The other Argo projects seems to do the same. The Argo Workflows and ArgoCD CLIs are normal CLIs and not kubectl plugins.

[dsbos]

It would also be helpful the documentation explained what exactly is needed for the CLI to actually function as a kubectl plug-in. (When I installed the CLI (per recent instructions), my kubectl command did not recognize the kubectl argo ... syntax.