Finally fixed rust-analyzer not carrying over `#[cfg(..)]` attributes when inserting imports into the file github.com/rust-lang/ru...

Progress! Most IDE features work now (notice syntax highlighting and inlay hints) and I've also added really bad whitespace insertion to make things more legible. There are some off by one errors in the mapping code though so some stuff breaks occasionally.

Okay this is more viable than I anticipated now I feel like I have to flesh this out. I think this is what you could label as actual first class IDE support for macros. I am astonished at how well this works.

Had some fun with prototyping a very cursed idea in rust-analyzer today.

The Shinkasen is a pretty cool experience I have to say (especially when you are used to the Deutsche Bahn)