fix(docker): implement entrypoint for env var support

Dockerfile

@@ -16,4 +16,6 @@ RUN apt update && apt install -y curl tar \
     && mv resvg /usr/local/bin/resvg \
     && chmod +x /usr/local/bin/resvg
 COPY --from=builder /app/svg-templater /usr/local/bin/svg-templater
-CMD ["svg-templater"]
+COPY entrypoint.sh /entrypoint.sh
+RUN chmod +x /entrypoint.sh
+ENTRYPOINT ["/entrypoint.sh"]

entrypoint.sh

@@ -0,0 +1,13 @@
+#!/bin/sh
+
+CMD="svg-templater"
+
+if [ -n "$API_KEY" ]; then
+    CMD="$CMD --frontendkey $API_KEY"
+fi
+
+if [ -n "$DATA_DIR" ]; then
+    CMD="$CMD --data $DATA_DIR"
+fi
+
+eval exec $CMD "$@"