chore: update CI to test against node v20

No change to logic. This updates GitHub actions CI to test on node v19
and v20.

Author: nfischer

.github/workflows/main.yml

@@ -23,6 +23,8 @@ jobs:
           - 16
           - 17
           - 18
+          - 19
+          - 20
         os:
           - ubuntu-latest
           - macos-latest

scripts/check-node-support.js

@@ -9,7 +9,7 @@ var shell = require('shelljs');
 
 // This is the authoritative list of supported node versions.
 var MIN_NODE_VERSION = 6;
-var MAX_NODE_VERSION = 18;
+var MAX_NODE_VERSION = 20;
 
 function checkReadme(minNodeVersion) {
   var start = '<!-- start minVersion -->';