cache node modules in CI

.github/workflows/nodejs.yml

@@ -23,7 +23,19 @@ jobs:
         uses: actions/setup-node@v1
         with:
           node-version: ${{ matrix.node-version }}
-      - run: npm install
+      - name: Use cached node_modules
+        id: cache
+        uses: actions/cache@v1
+        with:
+          path: node_modules
+          key: nodeModules-${{ hashFiles('**/yarn.lock') }}-${{ matrix.node-version }}
+          restore-keys: |
+            nodeModules-
+      - name: Install dependencies
+        if: steps.cache.outputs.cache-hit != 'true'
+        run: npm install
+        env:
+          CI: true
       - run: npm run prepare
       - run: npm test
         env: