Add Docker/Compose hosting with Caddy 2 reverse-proxy docs

Serves the static index.html via a small nginx container and documents
pointing an existing Caddy 2 instance (local or remote) at it via FQDN
with automatic HTTPS.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PbwKCCj1vwAoqgRYDoqgeL

docker/nginx.conf

@@ -0,0 +1,19 @@
+server {
+    listen 80;
+    server_name _;
+
+    root /usr/share/nginx/html;
+    index index.html;
+
+    gzip on;
+    gzip_types text/html text/css application/javascript;
+
+    location = /healthz {
+        return 200 "ok\n";
+        add_header Content-Type text/plain;
+    }
+
+    location / {
+        try_files $uri $uri/ /index.html;
+    }
+}