Add type hints for panel_id and __all__ in history panel for improved clarity

Author: JohananOppongAmoateng

debug_toolbar/panels/__init__.py

@@ -21,7 +21,7 @@ def __init__(self, toolbar, get_response):
     # Private panel properties
 
     @classproperty
-    def panel_id(cls):
+    def panel_id(cls) -> str:
         return cls.__name__
 
     @property

debug_toolbar/panels/history/__init__.py

@@ -1,3 +1,3 @@
 from debug_toolbar.panels.history.panel import HistoryPanel
 
-__all__ = [HistoryPanel.panel_id]
+__all__: list[str] = [HistoryPanel.panel_id]