feat: enable extra volume mounts for front end (#128)

This allows adding icons to generic events, e.g. add:

  extraVolumeMounts:
    - mountPath: /app/public/icons/eventc-icon.png
      name: icons
      subPath: eventc-icon.png
  extraVolumes:
    - name: icons
      configMap:
        name: icons

to the frontend section (and make a config map with your icon).

I added the icon config map via kustomize:

    configMapGenerator:
      - name: icons
        files:
          - eventc-icon.png

charts/keep/templates/frontend.yaml

@@ -91,6 +91,9 @@ spec:
             - name: state-volume
               mountPath: /state
               readOnly: false
+            {{- with .Values.frontend.extraVolumeMounts }}
+              {{- toYaml . | nindent 12 }}
+            {{- end }}
           {{- if .Values.frontend.healthCheck.enabled }}
           {{- toYaml .Values.frontend.healthCheck.probes | nindent 10 }}
           {{- end }}
@@ -118,4 +121,7 @@ spec:
       volumes:
         - name: state-volume
           emptyDir: {}
+        {{- with .Values.frontend.extraVolumes }}
+        {{- toYaml . | nindent 8 }}
+        {{- end }}
 {{- end }}