`marr standard list` only lists local standards and not available standards

[virtualian]

Describe the bug
marr standard list only lists local standards and not available standards,

To reproduce
Steps to reproduce:

1. Run marr standard list

Expected behavior
List all available standards and indicate which are installed or not. This list should not include all triggers. A new option e.g. marr standard details could provide more detail about a standard, including what triggers it.

[virtualian]

Check for overlap with other commands/options, e.g. marr init --project -s list