Add basic PR check

.github/workflows/pr-build-check.yaml

@@ -0,0 +1,20 @@
+name: check-build
+on:
+  pull_request:
+    branches:
+      - master
+
+jobs:
+  validate:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v2
+    - name: Setup Node.js
+      uses: actions/setup-node@v2
+      with:
+        node-version: '14.x'
+    - name: Validate build
+      run: |
+        yarn install
+        yarn run build