Use node 18 for eleventy build/deploy

Signed-off-by: David Martin <[email protected]>

.github/workflows/eleventy_build.yml

@@ -8,6 +8,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@master
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 18
+          cache: 'npm'
       - name: Build
         uses: TartanLlama/actions-eleventy@master
         with: