Update readme

Author: nghia-vo

README.md

@@ -108,6 +108,8 @@ Demonstrations
 - Calibrate a [fisheye](https://discorpy.readthedocs.io/en/latest/technical_notes/fisheye_correction.html) camera (GoPro Hero-8).
 
   ![GoPro_Hero8](https://github.com/DiamondLightSource/discorpy/raw/master/data/demo/fisheye_calibration.jpg)
+  ![GoPro_Hero8](https://github.com/DiamondLightSource/discorpy/raw/master/data/demo/fisheye_calibration_chessboard.jpg)
+  ![GoPro_Hero8](https://github.com/DiamondLightSource/discorpy/raw/master/data/demo/fisheye_calibration_dot_pattern.jpg)
 
 - Apply to a hazard camera of the [Mars Perseverance Rover](https://mars.nasa.gov/mars2020/multimedia/raw-images/).
   Details of how to estimate distortion coefficients of that camera without using