DOC: Add the sdl2 image lib in the requirements in the README file

README.md

@@ -30,6 +30,7 @@ For the module sdl2, you will need the folowing prerequisites:
 
 - the [mpv](https://mpv.io/) development library
 - the [sdl2](https://www.libsdl.org/) development library
+- the [sdl2-image](https://www.libsdl.org/projects/SDL_image/) development library
 
 For the module repo, you will need the folowing prerequisites: