feat: adding support for priority class name

[chrisjohnson00]

This adds the ability to define a priority class for the pod. This is implemented with backward comparability in mind, the priory class is only used if/when it is set in the values.yaml file.
My use case for this is:

• My cluster is designed for doing some CPU heavy batch jobs, which come and go as needed.
• When I have a large number of the batch jobs, sometimes I have game servers or other applications deployed that don't allow maximum cluster utilization by these batch jobs. Adding a non-default, lower priority to this deployment allows K8s to preempt my game server pods if other pods of a higher priority need the resources they are consuming.