Mention how to use a native class made in rust as a Reference by creating .gdnlib and .gdns files

There has been discussion about this here [godot-rust/#770](https://github.com/godot-rust/godot-rust/issues/770)

The idea is to write a tutorial so as to be able to do this from the gdscript side
```gdscript
extends Node

func _ready():
var x = MyNativeClass.new() # this is written in rust and can be a reference for instance
x.native_hello_world()
```

[This](https://hagsteel.com/posts/godot-rust/) has been mentioned to be a starting point.

I would be interested to do this and have some inputs unless @jacobsky is already on it?

---

_Edit Bromeon: fixed links_

Start with the discussion in godot-rust/#770 and the linked hagsteel.com tutorial. Write a tutorial explaining how to create .gdnlib and .gdns files and instantiate the Rust native class from GDScript as shown; done means the documented example is complete and usable from the GDScript side.

Written by the indexing model from the issue text.