add autoupdate (test probably broken)

.gitea/workflows/auto_update.yaml

@@ -0,0 +1,18 @@
+name: update the nix flake lock automatically every week
+run-name: update
+on:
+  schedule:
+    - cron: "0 4 * * 1"
+
+jobs:
+  update:
+    runs-on: ubuntu-latest
+    steps:
+      - name: get repo
+        uses: actions/checkout@v4.2.2
+
+      - name: install nix
+        uses: https://github.com/cachix/install-nix-action@v31
+
+      - name: run the update
+        run: nix flake update