[make release]: cosmetic addition.

Makefile

@@ -126,6 +126,11 @@ release:
 # Upload. (This automatically makes a .tar.gz archive available on gitlab.)
 	@ git push
 	@ git push --tags
+# Done.
+	@ echo "Done."
+	@ echo "If happy, please type:"
+	@ echo "  \"make publish\"   to publish a new opam package"
+	@ echo "  \"make export\"    to upload the documentation to yquem.inria.fr"
 
 .PHONY: publish
 publish: