Add node:20 to the allowed api runtimes configuration. Fixes issue #864

schema/staticwebapp.config.json

@@ -594,6 +594,7 @@
             "node:14",
             "node:16",
             "node:18",
+            "node:20",
             "python:3.8",
             "python:3.9",
             "python:3.10"