WebSocket and PyWorker fixes (#2366)

* WebSocket and PyWorker fixes

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

core/tests/javascript/ws/index.html

@@ -14,7 +14,7 @@
         print(event.type)
         ws.send("hello")
 
-    def onmessage(event):
+    async def onmessage(event):
         print(event.type, event.data)
         ws.close()