Add __bool__ for flags

discord/flags.py

@@ -159,6 +159,9 @@ class BaseFlags:
         max_value = -1 + (2**max_bits)
         return self._from_value(self.value ^ max_value)
 
+    def __bool__(self) -> bool:
+        return self.value != self.DEFAULT_VALUE
+
     def __eq__(self, other: object) -> bool:
         return isinstance(other, self.__class__) and self.value == other.value