Godot

Hello, I just wanted to make a small proposal to this wonderful crate. Namely, to improve the ergonomics for when using a custom build of godot.

Problem
The problem is as such, a user wants to use godot-rust with a custom build of godot so they need a custom build of gdnative-bindings to use godot-rust. The current process is nicely documented [here](https://godot-rust.github.io/book/a

the save name that is prefilled from the player species name doesn't update when the name is updated in the editor and the player directly goes to the pause menu (or at least the randomize button doesn't work like that).

Currently it looks like that:

We could use a UI theme there. I'd also rather use styleboxes and piggyback on button and similar nodes than use custom textures.

Issue description:

Instead of the boss controller just queue_freeing on death, it should do a deferred queue_free