Add Attributes to Shader.

assets/shader_programs/test_fragment.glsl

@@ -0,0 +1,5 @@
+#version 120
+
+void main() {
+        gl_FragColor = vec4(1, 1, 1, 1);
+}

assets/shader_programs/test_vertex.glsl

@@ -0,0 +1,7 @@
+#version 120
+
+attribute vec2 position;
+
+void main() {
+    gl_Position = vec4(position.x, position.y, 1.0, 1.0);
+}