ci: add node 20 to test matrix (#96)

Author: Fdawgs

.github/workflows/ci.yml

@@ -76,7 +76,7 @@ jobs:
       contents: read
     strategy:
       matrix:
-        node-version: [6, 8, 10, 11, 12, 13, 14, 15, 16, 18]
+        node-version: [6, 8, 10, 11, 12, 13, 14, 15, 16, 18, 20]
     steps:
       - name: Check out repo
         uses: actions/checkout@v3