chore(dependabot): set cooldown to 5 days (#139)

Wait 5 days after an update is live before Dependabot pushes a PR with the update. This is done to mitigate supply chain attacks.

Author: Schnouki

.github/dependabot.yml

@@ -7,6 +7,8 @@ updates:
       interval: weekly
       day: "monday"
       time: "00:00"
+    cooldown:
+      default-days: 5
     reviewers:
       - 'Doist/backend'
     commit-message:
@@ -18,6 +20,8 @@ updates:
       interval: weekly
       day: "monday"
       time: "00:00"
+    cooldown:
+      default-days: 5
     reviewers:
       - 'Doist/backend'
     commit-message: