Fix binary location and name and add web wasm support

[paddy-exe]

These changes make the library name consistent throughout the template when starting to work on a new GDExtension.

[addmix]

I was thinking of implementing some of these changes for myself. Any hold up for review and merge?

[paddy-exe]

I was thinking of implementing some of these changes for myself. Any hold up for review and merge?

I will need to reassess some parts of the changes I did first. I will get back to it this week hopefully.

[paddy-exe]

Superseded by https://github.com/godotengine/godot-cpp-template/pull/85