chore: update Node.js version in push.yml

Author: dziraf

.github/workflows/push.yml

@@ -10,7 +10,7 @@ jobs:
       - name: Setup
         uses: actions/setup-node@v1
         with:
-          node-version: '10.x'
+          node-version: '12.x'
       - uses: actions/cache@v1
         id: yarn-cache
         with:
@@ -47,4 +47,4 @@ jobs:
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           SLACK_WEBHOOK_URL: ${{ secrets.SLACK_WEBHOOK }}
-        if: always()
+        if: always()