Add Download to Dockerfile for more transparency

Dockerfile

@@ -1,8 +1,15 @@
 FROM python:alpine
 LABEL maintainer="mail+docker@f-brinker.de"
 
-# Insert Tileboard
-COPY ./files/ /tileboard/
+# Install wget
+RUN  apk update \                                                                                                                                                                                                                        
+    && apk add ca-certificates wget unzip \                                                                                                                                                                                                      
+    && update-ca-certificates    
+
+# Download TileBoard
+RUN wget -q -O release.zip "%RELEASE_URL%" \
+    && unzip release.zip -d /tileboard/ \
+    && rm release.zip
 
 # Start Server
 WORKDIR /tileboard