Create flake update job

.github/workflows/flake_update.yaml

@@ -0,0 +1,26 @@
+name: "flake_update"
+
+on:
+  schedule:
+    # At 7:00am on Monday
+    - cron: "0 7 * * 1"
+
+jobs:
+  flake_update:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Flake update
+        run: |
+          nix flake update
+
+      - name: Create Pull Request
+        uses: peter-evans/create-pull-request@v6
+        with:
+            commit-message: "Update flake.lock"
+            title: "Update flake.lock"
+            body: "This PR updates the flake.lock file."
+            branch: "update-flake-lock"
+            branch-suffix: "short-commit-hash"
+            base: "main"