Add json-schema for config file to templates for better IDE support

[SebastienGllmt]

With PaimaStudios/paima-engine#361 we can generate a json schema file for the config to use with intellisense. It might be nice to have this already placed in the templates so that most people start with this right away.

My main concern with that is that people might not know to update these json-config files if they update the Paima Engine version (which may have a breaking change for the config), but probably this can be solved by just explicitly mentioning in the changelog of new versions if people need to re-run this command