chore: make renovate detect dockerfile deps

Signed-off-by: Bence Csati <bence.csati@axoflow.com>

Dockerfile

@@ -1,5 +1,5 @@
 # Build the manager binary
-FROM golang:1.23 AS builder
+FROM golang:1.23.3-alpine3.20@sha256:25db3a0508ff009054bf467f25e1ab395fced0f93b69459dd736ae523e61c781 AS builder
 ARG TARGETOS
 ARG TARGETARCH
 
@@ -25,7 +25,7 @@ RUN CGO_ENABLED=0 GOOS=${TARGETOS:-linux} GOARCH=${TARGETARCH} go build -a -o ma
 
 # Use distroless as minimal base image to package the manager binary
 # Refer to https://github.com/GoogleContainerTools/distroless for more details
-FROM gcr.io/distroless/static:nonroot
+FROM gcr.io/distroless/static:nonroot@sha256:6cd937e9155bdfd805d1b94e037f9d6a899603306030936a3b11680af0c2ed58
 WORKDIR /
 COPY --from=builder /workspace/manager .
 USER 65532:65532