feat: add workflow for automatically updating

.forgejo/workflows/update-flake.yaml

@@ -0,0 +1,36 @@
+on:
+  schedule: '*/5 0 * * 1'
+
+jobs:
+  update-flake:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: https://github.com/cachix/install-nix-action@v26
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
+          github_access_token: '${{ secrets.GH_TOKEN }}'
+      - name: Create branch
+        run: git switch -c update/flake-lock
+      - name: Update flake.lock
+        run: nix flake update --commit-lock-file
+        env:
+          GIT_AUTHOR_NAME: kitchen-ci
+          GIT_AUTHOR_EMAIL: do-not-reply@buffets.kitchen
+          GIT_COMMITTER_NAME: kitchen-ci
+          GIT_COMMITTER_EMAIL: do-not-reply@buffets.kitchen
+      - name: Push to repo
+        run: git push -f origin update/flake-lock
+      - name: Create PR
+        run: >
+          curl -X POST "${{ env.GITHUB_API_URL }}/repos/${{ env.GITHUB_REPOSITORY }}/pulls"
+          --fail
+          -H "Content-Type: application/json"
+          -H "Authorization: token ${{ env.GITHUB_TOKEN }}"
+          -d '{
+               "title": "build(flake): update inputs",
+               "body": "",
+               "base": "main",
+               "head": "update/flake-lock",
+               "assignee: "chef"
+              }'