ci: add Forgejo Actions workflow for test automation

Runs TypeScript type checking and vitest on push/PR to master.

.forgejo/workflows/ci.yml

@@ -0,0 +1,22 @@
+name: CI
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Type check
+        run: npx tsc --noEmit
+
+      - name: Run tests
+        run: npm test