chore(build): remove legacy dependabot validate workflow; add clean script

Author: activescott

.github/workflows/dependabot-validate.yml

@@ -0,0 +1,5 @@
+#!/usr/bin/env sh
+THISDIR=$(cd $(dirname "$0"); pwd) #this script's directory
+THISSCRIPT=$(basename $0)
+
+git clean -f -d -x "$THISDIR"