add dependabot && flake update

.github/dependabot.yml

@@ -0,0 +1,6 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"

.github/workflows/update-flake-lock.yml

@@ -0,0 +1,23 @@
+name: "Update flakes"
+on:
+  repository_dispatch:
+  workflow_dispatch:
+  schedule:
+    - cron:  '38 0 * * 0,4'
+permissions:
+  pull-requests: write
+  contents: write
+jobs:
+  createPullRequest:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install Nix
+        uses: cachix/install-nix-action@v23
+        with:
+          github_access_token: ${{ secrets.GITHUB_TOKEN }}
+      - name: Update flake.lock
+        uses: DeterminateSystems/update-flake-lock@v20
+        with:
+          pr-labels: |                  # Labels to be set on the PR
+            merge-queue