Make available for godot 3

[raffomania]

Currently the asset is tagged as 2.1, making it unavailable from within an up-to-date godot editor.

[perdugames]

Currently the asset is tagged as 2.1, making it unavailable from within an up-to-date godot editor.

I am not working with Godot any more, but I believe it is not difficult to translate to Godot 3. If I remember, I used it in Godot 3 alpha. Feel free to translate to Godot 3 if you have to and send a pull.

[Calinou]

Note that Godot 3.1 will feature built-in support for OpenSimplex noise.