use button's label prop for its text

nicegui/elements/button.py

@@ -16,3 +16,6 @@ class Button(TextElement):
         self._props['color'] = 'primary'
 
         self.on('click', lambda _: handle_event(on_click, ClickEventArguments(sender=self, client=self.client)))
+
+    def _text_to_model_text(self, text: str) -> None:
+        self._props['label'] = text

nicegui/elements/mixins/text_element.py

@@ -10,7 +10,7 @@ class TextElement(Element):
     def __init__(self, *, text: str, **kwargs) -> None:
         super().__init__(**kwargs)
         self.text = text
-        self._text = text
+        self._text_to_model_text(text)
 
     def bind_text_to(self, target_object: Any, target_name: str = 'text', forward: Callable = lambda x: x):
         bind_to(self, 'text', target_object, target_name, forward)
@@ -29,5 +29,8 @@ class TextElement(Element):
         self.text = text
 
     def on_text_change(self, text: str) -> None:
-        self._text = text
+        self._text_to_model_text(text)
         self.update()
+
+    def _text_to_model_text(self, text: str) -> None:
+        self._text = text