Use Python-alpine and add docker doc.

Dockerfile

@@ -1,4 +1,4 @@
-FROM python:3.9
+FROM python:3.9-alpine
 
 WORKDIR /app
 

README.md

@@ -6,7 +6,30 @@ Netgear LTE Modem Exporter
 
 * Netgear LM1200
 
+# Config Example
+
+## Docker CLI
+
+    docker run -d --name lte-exporter \
+        -p 9877:9877 \
+        -e MODEM_HOST=192.168.5.1 \
+        -e MODEM_PASS=redtable654 \
+        ghcr.io/ncareau/netgear-lte-exporter:latest
+
+## Docker Compose
+
+    lte-exporter:
+        image: ghcr.io/ncareau/netgear-lte-exporter:latest
+        container_name: lte-exporter
+        environment:
+            - MODEM_HOST=192.168.5.1
+            - MODEM_PASS=redtable654
+        ports:
+            - 9877:9877
+        restart: unless-stopped
+
+
 # Thanks 
 
-https://github.com/amelchio/eternalegypt
-https://github.com/ickymettle/netgear_cm_exporter
+* https://github.com/amelchio/eternalegypt
+* https://github.com/ickymettle/netgear_cm_exporter