Update alpine Docker tag to v3.18.4 (#27)

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

Dockerfile

@@ -4,6 +4,6 @@ WORKDIR /src/cmd
 RUN apk add --no-cache git ca-certificates && \
   go build -v .
 
-FROM alpine:3.12.0
+FROM alpine:3.18.4
 COPY --from=builder /src/cmd /bin/godolint
 ENTRYPOINT ["/bin/godolint"]