Add Node 18 to workflow

Author: jdalton

.github/workflows/test.yml

@@ -24,5 +24,5 @@ jobs:
     with:
       no-lockfile: true
       npm-test-script: 'test-ci'
-      node-versions: '20,22'
+      node-versions: '18,20,22'
       os: 'ubuntu-latest,windows-latest'