add Caddy docker configuration

add Caddy Dockerfile to build image using xcaddy including cloudflare modules
docker-compose.yml file builds image instead of pulling it

caddy/Dockerfile

@@ -0,0 +1,9 @@
+FROM caddy:2.9.1-builder AS builder
+
+RUN xcaddy build \
+    --with github.com/caddy-dns/cloudflare \
+    --with github.com/WeidiDeng/caddy-cloudflare-ip
+
+FROM caddy:2.9.1
+
+COPY --from=builder /usr/bin/caddy /usr/bin/caddy