`list-images` should explain the filtering options

[ondrejbudai]

$ podman run --privileged  --rm ghcr.io/osbuild/image-builder-cli list-images --help
List buildable images, use --filter to limit further

Usage:
  image-builder list-images [flags]

Flags:
      --filter stringArray   Filter distributions by a specific criteria (e.g. "type:iot*")
  -h, --help                 help for list-images
      --output string        Output in a specific format (text, json)

Global Flags:
      --datadir string      Override the default data direcotry for e.g. custom repositories/*.json data
      --output-dir string   Put output into the specified direcotry

Expected:

I know which criteria can I use in the --filter flag.

(btw, IIRC criteria is a plural form, so the help test should contain either "by a specific criterion", or "by specific criteria".)