Add launcher CI workflow

.gitea/workflows/check.yml

@@ -0,0 +1,19 @@
+name: check
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+jobs:
+  launcher:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: "20"
+      - name: Validate launcher assets
+        run: |
+          jq empty app/manifest.json
+          node --check app/app.js