`#![feature]` may not be used on the stable release channel

[djkato]

Please update readme to recommend using:

cargo +nightly install --git https://github.com/siteforge-io/surreal-codegen.git

instead of

cargo install --git https://github.com/siteforge-io/surreal-codegen.git

#![feature(...)] cannot be used in the stable releases, and not everyone has nightly as their default toolchain :)

Also, is there a way to just get the entire schema.surqls types instead of my queries? I don't have query files, I write them in TS directly.