Added backgdrop, object and more text to text overlay example

data/shaders/textoverlay/background.vert

@@ -0,0 +1,17 @@
+#version 450
+
+#extension GL_ARB_separate_shader_objects : enable
+#extension GL_ARB_shading_language_420pack : enable
+
+layout (location = 0) out vec2 outUV;
+
+out gl_PerVertex 
+{
+    vec4 gl_Position;   
+};
+
+void main() 
+{
+	outUV = vec2((gl_VertexIndex << 1) & 2, gl_VertexIndex & 2);
+	gl_Position = vec4(outUV * vec2(2.0f, 2.0f) + vec2(-1.0f, -1.0f), 0.0f, 1.0f);
+}