added parameters

Author: ANKUR DWIVEDI

README.md

@@ -410,6 +410,8 @@ https://ik.imagekit.io/your_imagekit_id/tr:h-300,w-400,l-image,i-ik_canvas,bg-FF
 | effectUSM | e-usm |
 | effectContrast | e-contrast |
 | effectGray | e-grayscale |
+| effectShadow | e-shadow |
+| effectGradient | e-gradient |
 | original | orig |
 | raw | The string provided in raw will be added to the URL as it is. |