Use `COPY` instead of `ADD` in Dockerfile for folder

Ref:
https://docs.docker.com/develop/develop-images/#add-or-copy

Dockerfile

@@ -20,7 +20,7 @@ ARG AUTO_UPGRADE=1
 ENV AUTO_UPGRADE $AUTO_UPGRADE
 
 #Install
-ADD ./ /install_acme.sh/
+COPY ./ /install_acme.sh/
 RUN cd /install_acme.sh && ([ -f /install_acme.sh/acme.sh ] && /install_acme.sh/acme.sh --install || curl https://get.acme.sh | sh) && rm -rf /install_acme.sh/