Include documentation - list all installed languages including active #96

Feature Request

• Yes, I reviewed the contribution guidelines.

Describe your use case and the problem you are facing

When I list languages:

• I can filter installed with wp language core list --status=installed
• I can filter active with wp language core list --status=active

but I cannot return all installed languages at once, based on the documentation available

wp language list --status!=uninstalled
wp language list --status=active,installed

Describe the solution you'd like

A 'list all installed languages' variation should be explicit in the docs for language-command

• It is a common use-case to return *all* installed languages, especially with automation
• Fetching results for installed and then active and then concatenating both is clumsy
• I would like to reduce complexity and to use the closest-to-native approach