Add docker-compose & helm config

- Add docker-compose as well as instructions to run it locally with
  exposed ports 8080 & 8443 (with required nginx.conf additions)
- Add helm chart; it's pretty default and contains one template extension:
  we should be able to mount public/config.json from values.yaml (untested)

helm-chart/templates/tests/test-connection.yaml

@@ -0,0 +1,15 @@
+apiVersion: v1
+kind: Pod
+metadata:
+  name: "{{ include "element-call.fullname" . }}-test-connection"
+  labels:
+    {{- include "element-call.labels" . | nindent 4 }}
+  annotations:
+    "helm.sh/hook": test
+spec:
+  containers:
+    - name: wget
+      image: busybox
+      command: ['wget']
+      args: ['{{ include "element-call.fullname" . }}:{{ .Values.service.port }}']
+  restartPolicy: Never