Update install docs

Add docker-compose example

docs/install.md

@@ -187,6 +187,24 @@ docker run \
   serve
 ```
 
+Using docker-compose:
+```
+version: "2.1"
+
+services:
+  ntfy:
+    image: binwiederhier/ntfy
+    container_name: ntfy
+    command:
+      - serve
+    volumes:
+      - /var/cache/ntfy:/var/cache/ntfy
+      - /etc/ntfy:/etc/ntfy
+    ports:
+      - 80:80
+    restart: unless-stopped
+```
+
 Alternatively, you may wish to build a customized Docker image that can be run with fewer command-line arguments and without delivering the configuration file separately.
 ```
 FROM binwiederhier/ntfy