Define a values.schema.json for values.yaml files

**Is your feature request related to a problem?**
We would like to be able to validate a `values.yaml` file with `helm install`, `helm upgrade`, `helm lint`, `helm template`.
That would also enable importing a Helm chart from this repo with `cdk8s` to generate specific Helm construct to have type hinting.

**Is your feature request related to a specific Helm chart, if yes mention name of the chart?**
It is related to `aws-for-fluent-bit` but it would be great to have them for all the charts.

**Describe the solution you'd like**
The charts should have a `values.schema.json` JSON schma file.
See https://helm.sh/docs/topics/charts/#schema-files and https://github.com/cdk8s-team/cdk8s/blob/master/docs/cli/import.md#values-schema.

**Describe alternatives you've considered**
N/A

Start by inspecting the aws-for-fluent-bit chart's values.yaml and the Helm chart schema documentation linked in the issue. Define the corresponding values.schema.json and run helm lint, helm template, helm install, and helm upgrade validation; done means the chart's values.yaml is accepted and type hinting can use the schema.

Written by the indexing model from the issue text.