[example] cel-shading and outline using inverted hull

[ggrizzly]

Wanted to provide a cel-shading / outline example as that's relevant to a game project I'm working on. Didn't see one in examples, so here we are!

make shaders/shader_cel_shading in examples to test.

cel_shader_ex.mp4

[raysan5]

@ggrizzly thanks for the new example, looks great. Note that glsl120 and glsl100 versions of the shader should be provided to work on PLATFORM_WEB or platforms requiring OpenGL ES 2.0. Also, the screenshot for the example does not follow required size, it seems manually captured; note that you can press F12 to automatically capture the screen while running the example.

[ggrizzly]

@raysan5 Yeah I just manually screenshotted via the OS, but I can upload a proper screenshot. Good callout on the OpenGL versioning, will update as well - appreciate it!