Lets see if node_modules caching works

Author: mxstbr

.github/workflows/ci.yml

@@ -12,5 +12,15 @@ jobs:
     - uses: actions/setup-node@v1
       with: 
         node-version: 12.x
+    - name: Get yarn cache directory path
+      id: yarn-cache-dir 
+      run: echo "::set-output name=dir::$(yarn cache dir)"
+
+    - uses: actions/cache@v1
+      with:
+        path: ${{ steps.yarn-cache-dir.outputs.dir }}
+        key: ${{ runner.os }}-yarn-${{ hashFiles('**/yarn.lock') }}
+        restore-keys: |
+          ${{ runner.os }}-yarn-
     - run: yarn
     - run: yarn test --coverage