Add cooldown to dependabot.yaml

Add cooldown to dependabot.yaml  to address zizmor warning.
Setting 1 for default-days since zizmor does not enforce minimum thresholds (as long as it's not 0 or omitted).

Author: InessaPawson

.github/dependabot.yml

@@ -5,6 +5,8 @@ updates:
     directory: "/"
     schedule:
       interval: monthly
+    cooldown:
+      default-days: 1
     labels:
       - security
       - dependency-update