chore: add Dependabot configuration file (#17)

* Add Dependabot configuration file

Configure Dependabot for npm and GitHub Actions updates.

* Add automerge workflow for dependabot PRs

* Apply suggestion from @Copilot

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Apply suggestion from @jeswr

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: jeswr

.github/dependabot.yml

@@ -0,0 +1,11 @@
+version: 2
+
+updates:
+  - package-ecosystem: "npm"
+    directory: "/"
+    schedule:
+      interval: "daily"
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"

.github/workflows/automerge.yml

@@ -0,0 +1,18 @@
+name: Enable automerge on dependabot PRs
+
+on:
+  pull_request_target:
+
+jobs:
+  automerge:
+    name: Enable automerge on dependabot PRs
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      pull-requests: write
+    if: github.actor == 'dependabot[bot]'
+    steps:
+      - run: gh pr merge ${{ github.event.pull_request.html_url }} --auto --squash
+      - run: gh pr review ${{ github.event.pull_request.html_url }} --approve
+    env:
+      GH_TOKEN: ${{ github.token }}