add nginx.conf and improve readme

grafana/nginx.conf

@@ -0,0 +1,22 @@
+map $http_upgrade $connection_upgrade {
+  default upgrade;
+  '' close;
+}
+
+server {
+  server_name sudomain.your.domain;
+  location / {
+    proxy_pass http://localhost:3000/;
+  }
+
+  # Proxy Grafana Live WebSocket connections.
+  location /api/live {
+    proxy_http_version 1.1;
+    proxy_set_header Upgrade $http_upgrade;
+    proxy_set_header Connection "Upgrade";
+    proxy_set_header Host $http_host;
+    proxy_pass http://localhost:3002/;
+  }
+
+    listen 80;
+}