Docs: formatting issue for Sparkline.add_value

Add missing blank line in the docstring of Sparkline.add_value

Author: nicolasff

adafruit_display_shapes/sparkline.py

@@ -101,6 +101,7 @@ def clear_values(self) -> None:
 
     def add_value(self, value: float, update: bool = True) -> None:
         """Add a value to the sparkline.
+
         :param value: The value to be added to the sparkline
         :param update: trigger recreation of primitives