Improve Helm Chart

- use official v0.3.13 docker images hosted on GitHub
- load configs for Element-Call (public/config.json), nginx and SSL
  certs through ConfigMaps / PersistentVolumeClaims

config/nginx.conf

@@ -23,3 +23,33 @@ server {
     }
 }
 
+
+server {
+    listen 8443 ssl;
+    server_name mx22.local;
+    root   /app;
+
+    location / {
+        # disable cache entriely by default (apart from Etag which is accurate enough)
+        add_header Cache-Control 'private no-store, no-cache, must-revalidate, proxy-revalidate, max-age=0';
+        if_modified_since off;
+        expires off;
+        # also turn off last-modified since they are just the timestamps of the file in the docker image
+        # and may or may not bear any resemblance to when the resource changed
+        add_header Last-Modified "";
+
+        try_files $uri /$uri /index.html;
+    }
+
+    # assets can be cached because they have hashed filenames
+    location /assets {
+        expires 1w;
+        add_header Cache-Control "public, no-transform";
+    }
+
+    ssl_certificate "/etc/ssl/certs/element-call.crt";
+    ssl_certificate_key "/etc/ssl/private/element-call.key";
+    ssl_session_cache shared:SSL:1m;
+    ssl_session_timeout  10m;
+    ssl_prefer_server_ciphers on;
+}