chore(deps): update caddy docker tag to v2.9.1 (#19)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

Dockerfile

@@ -1,7 +1,7 @@
-FROM caddy:2.8.4-builder-alpine AS builder
+FROM caddy:2.9.1-builder-alpine AS builder
 
 RUN xcaddy build --with github.com/caddy-dns/cloudflare
 
-FROM caddy:2.8.4-alpine
+FROM caddy:2.9.1-alpine
 
 COPY --from=builder /usr/bin/caddy /usr/bin/caddy