Clarified docs about requirement to use command line tool to compile shaders.

bindings/bf/bgfx.bf

@@ -3005,6 +3005,8 @@ public static class bgfx
 	
 	/// <summary>
 	/// Create shader from memory buffer.
+	/// @remarks
+	///   Shader binary is obtained by compiling shader offline with shaderc command line tool.
 	/// </summary>
 	///
 	/// <param name="_mem">Shader binary.</param>