Bring in improvements from other gdnative libraries
Some other gdnative libraries have raised the bar quite a bit in terms of usability / user experience since this project was first created. I will list some examples:

- [ECMAScript](https://github.com/GodotExplorer/ECMAScript), [C#](https://github.com/godotengine/godot/tree/master/modules/mono), and [Python](https://github.com/touilleMan/godot-python) add entries to the attach script dialog:
![2020-09-01-10-58-53](https://user-images.githubusercontent.com/669012/91868198-7d282100-ec42-11ea-9f8c-1ff4995374bd.png)
- None of the above require creating `.gdns` files (or embedding in scenes)
- Of these, only C# seems to require a manifest file with each included script, but it generates the file automatically so I only noticed because of the git diff. Based on what I saw when experimenting, I'm guessing the "create script" action calls a method in the C# library which it uses as a trigger to generate or add to the file.
- godot-python is self-contained and available in the asset store (I know this one is a stretch and don't think it could be done with godot-nim, at least not easily)
- C# and ECMAScript don't even require a `.gdnlib` file

Are we able to add any of these improvements to this project?