Update Node.js version in GitHub Workflow

The Node.js version used in the npm-publish GitHub workflow has been updated. Previously, version 16.x was used, but it has now been updated to version 20.x, bringing it up-to-date with the latest Node.js version.

.github/workflows/npm-publish.yml

@@ -10,7 +10,7 @@ jobs:
       # Setup .npmrc file to publish to npm
       - uses: actions/setup-node@v3
         with:
-          node-version: '16.x'
+          node-version: '20.x'
           registry-url: 'https://registry.npmjs.org'
       - run: npm ci
       - run: npm publish