Fix the signal handling to work on Windows

This includes handling the SIGBREAK signal which is raised on Windows
resulting in the correct graceful shutdown.

Author: pgjones

src/quart/app.py

@@ -1371,11 +1371,9 @@ def run(
         def _signal_handler(*_: Any) -> None:
             shutdown_event.set()
 
-        try:
-            loop.add_signal_handler(signal.SIGTERM, _signal_handler)
-            loop.add_signal_handler(signal.SIGINT, _signal_handler)
-        except (AttributeError, NotImplementedError):
-            pass
+        for signal_name in {"SIGINT", "SIGTERM", "SIGBREAK"}:
+            if hasattr(signal, signal_name):
+                signal.signal(getattr(signal, signal_name), _signal_handler)
 
         server_name = self.config.get("SERVER_NAME")
         sn_host = None