Use Node.js 18 when publishing to NPM

Node.js version here shouldn't matter since the compatible versions are
specified in package.json and tested on other jobs.

Doesn't hurt to use the latest supported version.

.github/workflows/ci.yaml

@@ -81,7 +81,7 @@ jobs:
       - uses: actions/checkout@v3
       - uses: actions/setup-node@v3
         with:
-          node-version: 14
+          node-version: 18
           registry-url: https://registry.npmjs.org/
       - run: node --version
       - run: npm ci