Added frame buffer support.

assets/shaders/textured.frag

@@ -0,0 +1,13 @@
+#version 330 core
+
+in vec2 TexCoord;
+
+uniform sampler2D u_Text;
+
+out vec4 FragColor;
+
+void main() {
+  vec4 color = texture(u_Text, TexCoord);
+  FragColor = color + vec4(0.25, 0.25, 0.25, 1);
+  // FragColor = vec4(1, 0, 0, 1);
+}