ci: add typecheck step to GH actions

.github/workflows/lint.yml

@@ -1,11 +1,29 @@
-name: Lint
+name: Lint & Typecheck
 on:
   push:
     branches:
       - main
   pull_request:
 
 jobs:
+  typecheck:
+    name: Typecheck
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version-file: '.nvmrc'
+          cache: 'yarn'
+        env:
+          SKIP_YARN_COREPACK_CHECK: '1'
+      - name: Enable corepack
+        run: corepack enable
+      - name: Install dependencies
+        run: yarn
+      - name: Typecheck
+        run: yarn typecheck
+
   lint:
     name: Lint
     runs-on: ubuntu-latest