Support for `justfile` and `.just` files

[PaulRBerg]

Clear and concise description of the problem

add support for the just CLI

Suggested solution

justfile and *.just files should be nested

Validations

• Follow our Code of Conduct
• Read the Contributing Guide.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[antfu]

Feel free to PR! Thanks