Include Node 21 in test matrix

Author: rien

.github/workflows/ci.yml

@@ -13,7 +13,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        node-version: [^14.19, ^16.15, ^18, ^20]
+        node-version: [^14.19, ^16.15, ^18, ^20, ^21]
         os: [ubuntu-latest, windows-latest]
     steps:
       - uses: actions/checkout@v3