add node v20 to CI (#546)

Author: bh2smith

.github/workflows/CI.yml

@@ -9,7 +9,7 @@ jobs:
   test:
     strategy:
       matrix:
-        node: [16.x]
+        node: [16.x, 20.x]
         os: [ubuntu-latest]
     runs-on: ${{ matrix.os }}
     steps: