fix: use yarn instead of npm on GitHub Action

Author: KushibikiMashu

.github/workflows/node.js.yml

@@ -16,14 +16,14 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [12.x, 14.x]
+        node-version: [14.x]
 
     steps:
     - uses: actions/checkout@v2
     - name: Use Node.js ${{ matrix.node-version }}
       uses: actions/setup-node@v1
       with:
         node-version: ${{ matrix.node-version }}
-    - run: npm ci
-    - run: npm test
-    - run: npm run build --if-present
+    - run: yarn install --frozen-lockfile
+    - run: yarn test
+    - run: yarn build