issue-208 Add support for Custom POD Annotations

[maddisondavid]

Change log description
Updates the Helm chart to allow custom annotations to be expressed on the final Schema registry PODs

Purpose of the change
Fixes #208

What the code does
Provides a podAnnotations value on the Helm chart allowing custom POD annotations to be expressed. The value of the podAnnotations is copied to the final deployment template

How to verify it
Using the following values file called "values.txt"

podAnnotations:
  first: one
  second: two

helm install schema-registry charts/schema-registry --values values.txt The following shows the final output:

spec:
  progressDeadlineSeconds: 600
  replicas: 2
  revisionHistoryLimit: 10
  selector:
    matchLabels:
      app.kubernetes.io/name: schema-registry
  strategy:
    rollingUpdate:
      maxSurge: 25%
      maxUnavailable: 25%
    type: RollingUpdate
  template:
    metadata:
      annotations: <<<<<<<<<<<<<<<<<
        first: one
        second: two
      creationTimestamp: null
      labels:
        app.kubernetes.io/name: schema-registry

With no custom POD annotations specified:

  template:
    metadata:
      creationTimestamp: null
      labels:
        app.kubernetes.io/name: schema-registry
    spec:

[maddisondavid]

README updated and all commits signed-off