add vertexarray, move Sandbox::Demolayer code to EditorLayer

Editor/assets/shaders/demo.glsl

@@ -0,0 +1,29 @@
+#type vertex
+#version 430 core
+
+layout(location = 0) in vec3 a_Position;
+layout(location = 1) in vec3 a_Normal;
+
+uniform mat4 u_MVP;
+
+out vec3 v_Normal;
+
+void main()
+{
+	gl_Position = u_MVP * vec4(a_Position, 1.0);
+    v_Normal = a_Normal;
+}
+
+#type fragment
+#version 430 core
+
+layout(location = 0) out vec4 o_Color;
+
+uniform vec4 u_Color;
+in vec3 v_Normal;
+
+void main()
+{
+    o_Color = u_Color * vec4(v_Normal * 0.5 + 0.5, 1.0f);
+	// o_Color = vec4(0.6, 0.7, 0.8, 1.0);
+}