ci: add typechecking CI job

Author: ndhoule

.github/workflows/typecheck.yml

@@ -0,0 +1,25 @@
+---
+name: Typecheck
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
+jobs:
+  typecheck:
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 18.14.0
+          cache: npm
+
+      - name: Install dependencies
+        run: npm ci --no-audit
+
+      - name: Typecheck
+        run: npm run typecheck