Configure Dependabot for npm with monthly updates

Updated Dependabot configuration to use npm and change update schedule to monthly.

Author: marlo-longley

.github/dependabot.yml

@@ -0,0 +1,12 @@
+# To get started with Dependabot version updates, you'll need to specify which
+# package ecosystems to update and where the package manifests are located.
+# Please see the documentation for all configuration options:
+# https://docs.github.com/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file
+
+version: 2
+updates:
+  # Keep npm dependencies up to date
+  - package-ecosystem: "npm"
+    directory: "/"
+    schedule:
+      interval: "monthly"