Improve documentation on kuberenetes deployment properites

[markpollack]

Many of the kubernetes deployment property keys take a JSON string as their value. This creates a bit of friction as all examples that are cut-n-pasted from k8s docs that are in YAML. Volume mounts are a good example. The JavaDoc for the deployer has many examples that should be surfaced in dataflow.spring.io, e.g. https://github.com/spring-cloud/spring-cloud-deployer-kubernetes/blob/main/src/main/java/org/springframework/cloud/deployer/spi/kubernetes/DeploymentPropertiesResolver.java#L117

[corneil]

Updating reference documentation on Getting Started for Kubernetes to point to the Configuration - Kubernetes section which has information on the deployment properties.