Added leniency to the code (#33)

Co-authored-by: ceprio <c.git@pronovost.net>

webruntime/_common.py

@@ -93,9 +93,21 @@ def __init__(self, **kwargs):
         atexit.register(self.close)
 
         # Increase chance of closing runtime when Python is forced to stop
-        signal.signal(signal.SIGTERM, self.close)
-        signal.signal(signal.SIGINT, self.close)
-
+        try:
+            signal.signal(signal.SIGTERM, self.close)
+        except ValueError as e:  # Cannot use signal.signal outside of main thread
+            if str(e) != 'signal only works in main thread':
+                raise
+            else:
+                pass  # Continue as it will still work on some browser (like Chrome)
+        try:
+            signal.signal(signal.SIGINT, self.close)
+        except ValueError as e:    # Cannot use signal.signal outside of main thread
+            if str(e) != 'signal only works in main thread':
+                raise
+            else:
+                pass  # Continue as it will still work on some browser (like Chrome)
+
         self._exe = None
         self._version = None
         self._proc = None