Allow to register custom chasers in Maya

In AYON Maya addon, the current way to add chasers is by modifying the code base and add the chasers manually to this function.

I believe it’d be cool to have a setting in AYON Maya addon where admins can add paths to custom chasers that will be regisetered on starting Maya.

Bouns: Resolve the paths with environment variables or template keys to allow such keys like `{studio_configs}` or `{root[configs]}`