add auto clean

Dockerfile

@@ -5,6 +5,9 @@ RUN apt update
 RUN DEBIAN_FRONTEND=noninteractive \
 apt install nginx php8.1 php8.1-fpm php8.1-gd -y
 
+# Clean up
+RUN apt clean
+
 # Set up nginx
 COPY ./docker/nginx.conf /etc/nginx/nginx.conf