[FEATURE] Add command to list K3s image tags

[nunix]

Scope of your request

• a new flag for a command (e.g. k3d cluster create --<your-flag>)?
  • k3d version list-k3s

Describe the solution you'd like

In order to help users creating a cluster with a specific K3s version, a new command could list the available versions.
In comparison, Rancher Desktop has a selection in their GUI. As k3d is command based, a shorter listing of versions could be needed/helpful.

Based on the current command hierarchy, my suggestion is to have k3d version list-k3s (or something similar).
Initially I thought about a subcommand in the image option, however it would have mixed purposes.

Describe alternatives you've considered

Currently I have two different ways of getting the K3s versions:

• Go to hub.docker.com and look the image tags there
• Use regctl created by a Docker Captain: regctl tag list rancher/k3s

Hope it makes sense and let me know if you need any further information.

Keep the excellent work.
The Corsair