Update ci.yml

Author: iamareebjamal

.github/workflows/ci.yml

@@ -17,6 +17,16 @@ jobs:
       uses: actions/setup-node@v1
       with:
         node-version: 14.x
+    - name: Get yarn cache path
+      id: yarn-cache-path
+      run: echo "::set-output name=dir::$(yarn cache dir)"
+    - uses: actions/cache@v2
+      id: yarn-cache
+      with:
+        path: ${{ steps.yarn-cache-path.outputs.dir }}
+        key: ${{ runner.os }}-yarn-${{ hashFiles('**/yarn.lock') }}
+        restore-keys: |
+          ${{ runner.os }}-yarn
     - run: yarn
     - run: touch .env
     - run: yarn l10n:generate