actions: update Node.js LTS because 11ty requires a higher version

Author: joshtynjala

.github/workflows/build.yml

@@ -12,7 +12,7 @@ jobs:
       - uses: actions/checkout@v3
       - uses: actions/setup-node@v3
         with:
-          node-version: 16
+          node-version: 20
       - name: Install dependencies
         run: npm ci
       - name: Build website