Add missing or (if it's there) improve module information in documentation

[Thermatix]

I'm trying to figure things out and I'm struggling to find the following information

• How to refer to module tasks from other modules (for task dependencies)
• How to refer to tasks in the parent file (I.e. super::task_name)
• sub-module settings
• Variables defined in other files or in parent (or via import statements)
  There was a few other's but I can't recall now.

Some of the things are mentioned in Modules stabilization tracking issue #929, some of them are mentioned at the top but with no actual "This is how you do this" under each item (nor I can't find it within the thread itself).

Also for the top two I did find this: Dependency from a parent/child justfile

P.s.

I get syntax errors when I try something like task: super::task

[casey]

Modules are definitely incomplete at the moment. See #2252, and feel free to comment there or open individual issues if something is missing.