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/models/resources/shaders/cubemap.fs

@@ -0,0 +1,38 @@
+/*******************************************************************************************
+*
+*   rPBR [shader] - Equirectangular to cubemap fragment shader
+*
+*   Copyright (c) 2017 Victor Fisac
+*
+**********************************************************************************************/
+
+#version 330
+
+// Input vertex attributes (from vertex shader)
+in vec3 fragPos;
+
+// Input uniform values
+uniform sampler2D equirectangularMap;
+
+// Output fragment color
+out vec4 finalColor;
+
+vec2 SampleSphericalMap(vec3 v)
+{
+    vec2 uv = vec2(atan(v.z, v.x), asin(v.y));
+    uv *= vec2(0.1591, 0.3183);
+    uv += 0.5;
+    return uv;
+}
+
+void main()
+{
+    // Normalize local position 
+    vec2 uv = SampleSphericalMap(normalize(fragPos));
+
+    // Fetch color from texture map
+    vec3 color = texture(equirectangularMap, uv).rgb;
+
+    // Calculate final fragment color
+    finalColor = vec4(color, 1.0);
+}