Update pkg.yml

Author: tacxou

.github/workflows/pkg.yml

@@ -14,6 +14,7 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: '18'
+      - run: npm install -g yarn
       - run: yarn --frozen-lockfile
       - run: npm install --global pkg
       - run: yarn build