merge vertexbuffer and indexbuffer to buffer.cpp/h file

Sandbox/assets/shaders/shader.glsl

@@ -13,7 +13,9 @@ void main()
 
 layout(location = 0) out vec4 o_Color;
 
+uniform vec4 u_Color;
+
 void main()
 {
-	o_Color = vec4(1.0, 0.0, 1.0, 1.0);
+	o_Color = u_Color;
 }