chore(ci): add node 21.x to build matrix

Author: glennsl

.github/workflows/nodejs.yml

@@ -15,7 +15,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [18.x, 20.x]
+        node-version: [18.x, 20.x, 21.x]
       fail-fast: false
 
     steps: