Renaming calculator to counter in example

Author: darrenburns

docs/examples/guide/widgets/calculator.py renamed to docs/examples/guide/widgets/counter.py

@@ -21,8 +21,8 @@ def action_change_count(self, amount: int) -> None:
         self.count += amount
 
 
-class CalculatorApp(App[None]):
-    CSS_PATH = "calculator.tcss"
+class CounterApp(App[None]):
+    CSS_PATH = "counter.tcss"
 
     def compose(self) -> ComposeResult:
         yield Counter()
@@ -31,5 +31,5 @@ def compose(self) -> ComposeResult:
 
 
 if __name__ == "__main__":
-    app = CalculatorApp()
+    app = CounterApp()
     app.run()