chore: update Dockerfile

Author: ldez

buildx.Dockerfile

@@ -1,9 +1,11 @@
 # syntax=docker/dockerfile:1.4
 FROM alpine:3
 
+ARG TARGETPLATFORM
+
 RUN apk --no-cache --no-progress add git ca-certificates tzdata jq \
     && rm -rf /var/cache/apk/*
 
-COPY traefik-certs-cleaner /usr/bin/traefik-certs-cleaner
+COPY $TARGETPLATFORM/traefik-certs-cleaner /usr/bin/traefik-certs-cleaner
 
 ENTRYPOINT ["/usr/bin/traefik-certs-cleaner"]