Add Litecoin MWEB docker fragment (#974)

* Add MWEB docker fragment

* Add container name

docker-compose-generator/docker-fragments/opt-add-ltcmweb.yml

@@ -0,0 +1,16 @@
+version: "3"
+
+services:
+  btcpayserver:
+    environment:
+      BTCPAY_LTC_MWEB_DAEMON_URI: http://mwebd:12345
+  mwebd:
+    restart: unless-stopped
+    container_name: mwebd
+    image: hectorchu1/mwebd
+    volumes:
+      - "mwebd_datadir:/data"
+volumes:
+  mwebd_datadir:
+required:
+  - "litecoin"