Add Spinner, a Minecraft hostname-routing reverse proxy

Routes Java Edition connections by the hostname in the handshake, with
wildcard domains, backend failover, PROXY protocol v2, cached server-list
status from health probes, hot-reloaded config, and an admin page and
metrics endpoint. Includes CI, tagged releases and a container image.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

deploy/docker-compose.yml

@@ -0,0 +1,19 @@
+# Run Spinner with Docker:
+#   cp .env.example .env     (then set SPINNER_ADMIN_TOKEN)
+#   docker compose up -d
+#
+# On first start Spinner writes a starter config to /data/spinner.json. Add servers from the
+# admin page on port 8080, or edit the file in the volume. Keep 8080 private or behind HTTPS.
+services:
+  spinner:
+    image: git.veillax.com/veillax/spinner:latest
+    restart: unless-stopped
+    env_file: .env
+    ports:
+      - "25565:25565"
+      - "127.0.0.1:8080:8080"
+    volumes:
+      - spinner-data:/data
+
+volumes:
+  spinner-data: