get_node() function should have generics in TypeScript

In C#, we are able to use the simplest and nice `` as a shortcut and cleaner version of `(T)` or `as` to convert the Node into other class that is inherited to Node:
```csharp
private Sprite sprite;

public override void _Ready()
{
sprite = GetNode("path/to/sprite");
}
```
But in typescript, we are not allowed to write `` or generics to `get_node()` like in C#. Instead, we use `as` to convert the Node into other class that is inherited to Node.
```typescript
private sprite: godot.Sprite;

public override _ready(): void {
this.sprite = this.get_node('path/to/sprite') as godot.Sprite;
}
```
I'd make a workaround by editing the godot.d.ts but it would be nice if it's built-in to the module.

Comienza en godot.d.ts y localiza la declaración de get_node() descrita en el issue. Actualiza esa declaración para que los llamadores puedan proporcionar un genérico de TypeScript para el tipo Node devuelto y, después, verifica que el ejemplo ya no necesite un as cast.

Escrito por el modelo de indexación a partir del texto del issue.