Update Dockerfile

Dockerfile

@@ -102,4 +102,10 @@ COPY src/replays/*        /app/danser/custom-replays/
 COPY src/settings/*       /app/danser/settings/
 COPY src/default-skin/    /app/danser/skins/default-skin/
 
+RUN groupadd -g 1000 appuser && \
+    useradd -u 1000 -g 1000 -m -s /bin/bash appuser && \
+    chown -R 1000:1000 /app
+
+USER 1000:1000
+
 WORKDIR /app/danser