`trestle task` should allow list without a valid trestle directory.

[butler54]

Describe the bug

trestle task -l requires you to be in a valid directory.

To Reproduce

Run trestle task -l and see an error for the fact it's not inside a trestle project.

Expected behavior

As a help function I would expect this to operate without a check for a trestle project setup.

Screenshots / Logs.

N.A.

Environment

• trestle 3.3.0