Add comment for why we're adding reusable workflows to the autobuild script

Author: mrecachinas

actions/extractor/tools/autobuild.sh

@@ -2,6 +2,10 @@
 
 set -eu
 
+# Note: We're adding the `reusable_workflows` subdirectories to proactively
+# record workflows that were called cross-repo, check them out locally,
+# and enable an interprocedural analysis across the workflow files.
+# These workflows follow the convention `.github/reusable_workflows/<nwo>/*.ya?ml`
 DEFAULT_PATH_FILTERS=$(cat << END
 exclude:**/*
 include:.github/workflows/*.yml