change node version for github actions

Author: yosang

.github/workflows/main.yaml

@@ -7,7 +7,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v1
         with:
-          node-version: "14" 
+          node-version: '20' 
       - run: npm install
       - run: npm run format
       - run: npm run lint