chore: add Dependabot config for npm and GitHub Actions

Activates the existing dependabot-automerge workflow by configuring
weekly update schedules for the root npm package, the demo app, and
GitHub Actions. Minor/patch updates are grouped per ecosystem to keep
PR volume manageable; majors stay separate so the auto-merge workflow
leaves them for manual review.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: zhawtof

.github/dependabot.yml

@@ -0,0 +1,45 @@
+version: 2
+updates:
+  - package-ecosystem: npm
+    directory: /
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 10
+    groups:
+      dev-dependencies:
+        dependency-type: development
+        update-types:
+          - minor
+          - patch
+      production-dependencies:
+        dependency-type: production
+        update-types:
+          - minor
+          - patch
+
+  - package-ecosystem: npm
+    directory: /demo
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 5
+    groups:
+      dev-dependencies:
+        dependency-type: development
+        update-types:
+          - minor
+          - patch
+      production-dependencies:
+        dependency-type: production
+        update-types:
+          - minor
+          - patch
+
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly
+    groups:
+      actions:
+        update-types:
+          - minor
+          - patch