Provide Helm chart JSON schema

[smyrick]

Is your feature request related to a problem? Please describe.

The router.yaml has a JSON config schema that can be generated from the Router binary but the helm charts provided by the router team do not have a JSON validation schema

https://www.apollographql.com/docs/router/containerization/kubernetes/#about-the-router-helm-chart

Describe the solution you'd like

Provide the mapping JSON schema for the helm charts

Describe alternatives you've considered

I could use helm validators on my PR jobs to make sure everything works but it would be nice to do this in my IDE or use the JSON schema in my PR to do the validation steps