WIP: cache

.github/workflows/ci.yml

@@ -378,6 +378,12 @@ jobs:
     steps:
     - uses: actions/checkout@v2
 
+    - uses: actions/setup-node@v2
+      with:
+        node-version: ${{ matrix.node-version }}
+        cache: 'yarn'
+        cache-dependency-path: '**/yarn.lock'
+
     - name: Cache/Restore node_modules
       id: cache-dependencies
       uses: actions/cache@v2