Add github action.

Author: robinheghan

.github/workflows/test.yml

@@ -0,0 +1,29 @@
+name: Test
+
+on:
+  pull_request:
+    branches: [main]
+  push:
+    branches: [main]
+
+jobs:
+  run-tests:
+    strategy:
+      matrix:
+        os: [ubuntu-latest]
+
+    runs-on: ${{ matrix.os }}
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install devbox
+        uses: jetify-com/[email protected]
+        with:
+          enable-cache: true
+
+      - name: Verify formatting
+        run: devbox run format:check
+
+      - name: Run tests
+        run: devbox run -- gren make