Is your feature request related to a problem? Please describe.

I propose adding ci or similar to the list of shortNames in the clusterissuers.cert-manager.io CRD.

Similar to #311, repeatedly typing clusterissuers is not particularly friendly.

Would you accept a patch to the CRD to implement this? I'm not Sure if there is any value in adding it to the helm chart as was done with the certificate short name.

Describe the solution you'd like

Typing something shorter than clusterissuers ;)

Additional context

It is common for CRD providers to include short names for resources with long names, it would be good to shorten this one.

/kind feature