`yarn build` in ci

.github/workflows/build.yml

@@ -0,0 +1,25 @@
+name: Build
+on: [push]
+jobs:
+  test:
+    name: Build on Node ${{ matrix.node }} and ${{ matrix.os }}
+
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        node: ["14.x"]
+        os: [ubuntu-latest]
+
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v2
+
+      - name: Use Node ${{ matrix.node }}
+        uses: actions/setup-node@v1
+        with:
+          node-version: ${{ matrix.node }}
+
+      - name: Install deps
+        uses: bahmutov/npm-install@v1
+
+      - run: yarn build