multi: add release helper docker file

dev.Dockerfile

@@ -1,3 +1,9 @@
+# If you change this value, please change it in the following files as well:
+# /.travis.yml
+# /Dockerfile
+# /make/builder.Dockerfile
+# /.github/workflows/main.yml
+# /.github/workflows/release.yml
 FROM golang:1.15.6-alpine as builder
 
 LABEL maintainer="Olaoluwa Osuntokun <laolu@lightning.engineering>"