Add mage to project dependencies

What does this MR do?

Adds mage as a project dependencies when running mise install so mage commands like mage k8s:generatePermissionsDocs are more easily runnable.

Why was this MR needed?

I had to run mage k8s:generatePermissionsDocs, but didn't have mage installed. I tried mise install but it didn't install mage.

What's the best way to test this MR?

1. Check out this branch.
2. Run mise install.
3. Run a mage target. You can run which mage to check you're running the mise-installed binary.