updated readme
updated readme

- explain the differences of GDNative and NativeScripts
- improve readability of instructions to get started
- update the FAQ section. let it take less space and push to the end of
the readme.
- added hyperlinks to C++ and D bindings. Rust soon?

ShadowApex/godot-go,ShadowApex/go-godot,ShadowApex/godot-go,ShadowApex/godot-go,ShadowApex/godot-go,ShadowApex/go-godot