Add a note about cursor blink animation energy consumption

kitty/options/definition.py

@@ -337,6 +337,8 @@
 it will go from opaque to transparent and then back again over the next half. You can specify
 different easing functions for the two halves, for example: :code:`-1 linear ease-out`. kitty
 supports all the :link:`CSS easing functions <https://developer.mozilla.org/en-US/docs/Web/CSS/easing-function>`.
+Note that turning on animations uses extra power as it means the screen is redrawn multiple times
+per blink interval. See also, :opt:`cursor_stop_blinking_after`.
 '''
     )