Use cooldown for dependabot, adds github-actions to dependabot

Author: zachleat

.github/dependabot.yml

@@ -5,12 +5,23 @@
 
 version: 2
 updates:
-  - package-ecosystem: "npm" # See documentation for possible values
-    directory: "/" # Location of package manifests
+  - package-ecosystem: "npm"
+    directory: "/"
     schedule:
-      interval: "weekly"
+      interval: weekly
+    cooldown:
+      default-days: 7
     labels:
       - "dependency-updates"
     versioning-strategy: increase
     allow:
       - dependency-type: "production"
+    assignees: [zachleat]
+
+  - package-ecosystem: github-actions
+    directories: ".github/workflows/**"
+    schedule:
+      interval: weekly
+    cooldown:
+      default-days: 7
+    assignees: [zachleat]