Generate docs using https://github.com/hashicorp/terraform-plugin-docs

[Breee]

I want to suggest that we generate documentation according to:

https://developer.hashicorp.com/terraform/registry/providers/docs#generating-documentation

Such that (1) we have always up to date documentation and (2) enable the usage of the latest https://github.com/upbound/upjet-provider-template/ (e.g. due to https://github.com/upbound/upjet-provider-template/issues/32 as they seem to depend on https://github.com/hashicorp/terraform-plugin-docs/)