Create dart.yml

.github/workflows/dart.yml

@@ -0,0 +1,15 @@
+name: "Build Flatpak"
+on:
+  workflow_dispatch:
+  push:
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - uses: cachix/install-nix-action@v27
+    - run: nix develop --command just flatpak-build
+    - uses: actions/[email protected]
+      with:
+        name: quad.flatpak
+        path: build/quad.flatpak