Changing examples to use makefile

- Testing a modified version of the makefile from raylib Instead of multiple project files for examples.
- Fixed readme example

Examples/shaders/resources/shaders/glsl100/posterization.fs

@@ -0,0 +1,29 @@
+#version 100
+
+precision mediump float;
+
+// Input vertex attributes (from vertex shader)
+varying vec2 fragTexCoord;
+varying vec4 fragColor;
+
+// Input uniform values
+uniform sampler2D texture0;
+uniform vec4 colDiffuse;
+
+// NOTE: Add here your custom variables
+
+float gamma = 0.6;
+float numColors = 8.0;
+
+void main() 
+{ 
+    vec3 color = texture2D(texture0, fragTexCoord.xy).rgb;
+    
+    color = pow(color, vec3(gamma, gamma, gamma));
+    color = color*numColors;
+    color = floor(color);
+    color = color/numColors;
+    color = pow(color, vec3(1.0/gamma));
+    
+    gl_FragColor = vec4(color, 1.0);
+}