imp: add initial GH actions

.github/dependabot.yml

@@ -0,0 +1,13 @@
+version: 2
+updates:
+
+  - package-ecosystem: github-actions
+    directory: "/"
+    schedule:
+      interval: daily
+      time: '00:00'
+      timezone: UTC
+    open-pull-requests-limit: 10
+    commit-message:
+        prefix: "chore"
+        include: "scope"

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

@@ -0,0 +1,19 @@
+name: update-flake-lock
+on:
+  workflow_dispatch: # allows manual triggering
+  schedule:
+    - cron: '0 0 * * 0' # runs weekly on Sunday at 00:00
+
+jobs:
+  lockfile:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+      - name: Install Nix
+        uses: cachix/install-nix-action@v17
+        with:
+          extra_nix_config: |
+            access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}
+      - name: Update flake.lock
+        uses: DeterminateSystems/update-flake-lock@v9