Enable Dependabot version updates

Creates dependabot.yml configured to run version update scans every Monday at 9am London time.

.github/dependabot.yml

@@ -0,0 +1,32 @@
+# 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:
+  # Maintain dependencies for yarn
+  - package-ecosystem: "npm" # works for yarn
+    directory: "/" # Location of package manifests
+    schedule:
+      interval: "weekly"
+      time: "09:00"
+      timezone: "Europe/London"
+
+  # Maintain dependencies for GitHub Actions
+  - package-ecosystem: "github-actions"
+    # Workflow files stored in the default location of `.github/workflows`. (You don't need to specify `/.github/workflows` for `directory`. You can use `directory: "/"`.)
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      time: "09:00"
+      timezone: "Europe/London"
+
+  # Maintain dependencies for bundler
+  - package-ecosystem: "bundler"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      time: "09:00"
+      timezone: "Europe/London"
+