Add dependabot

Add dependabot configuration file.

Author: martincostello

.github/dependabot.yml

@@ -0,0 +1,18 @@
+version: 2
+updates:
+- package-ecosystem: "github-actions"
+  directory: "/"
+  groups:
+    actions:
+      patterns:
+        - actions/*
+  schedule:
+    interval: monthly
+    time: "06:30"
+    timezone: Europe/London
+- package-ecosystem: "npm"
+  directory: "/"
+  schedule:
+    interval: monthly
+    time: "06:30"
+    timezone: Europe/London