add node 18 to GA

Author: icebob

.github/workflows/nodejs.yml

@@ -8,7 +8,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [12.x, 14.x, 16.x]
+        node-version: [12.x, 14.x, 16.x, 18.x]
 
     steps:
     - uses: actions/checkout@v1