add syncthing to stack

roles/docker/templates/syncthing-compose.yml.j2

@@ -0,0 +1,25 @@
+services:
+  syncthing:
+    image: syncthing/syncthing
+    container_name: syncthing
+    hostname: my-syncthing
+    environment:
+      - PUID=1000
+      - PGID=1000
+    volumes:
+      - home:/var/syncthing
+    ports:
+      - 100.70.169.99:8384:8384 # Web UI
+      - 100.70.169.99:22000:22000/tcp # TCP file transfers
+      - 100.70.169.99:22000:22000/udp # QUIC file transfers
+      - 100.70.169.99:21027:21027/udp # Receive local discovery broadcasts
+    restart: unless-stopped
+    healthcheck:
+      test: curl -fkLsS -m 2 127.0.0.1:8384/rest/noauth/health | grep -o --color=never OK || exit 1
+      interval: 1m
+      timeout: 10s
+      retries: 3
+
+volumes:
+  home:
+