Use proc_macro instead of proc_macro_hack when supported

[Scoder12]

The macros using proc_macro_hack don't work with Rust Analyzer ( rust-lang/rust-analyzer#6835 ).

From the proc-macro-hack repo:

Note: As of Rust 1.45 this crate is superseded by native support for #[proc_macro] in expression position. Only consider using this crate if you care about supporting compilers between 1.31 and 1.45.

If supported older compilers is important, it is possible to use build cfg attrs to conditionally use proc_macro only when it is supported. Here is an example of a PR that does that: rust-lang/futures-rs#2407

If supporting older compilers isn't a concern, proc_macro_hack can simply be replaced with proc_macro.

[Scoder12]

BTW, thank you so much for maintaining this library, it is awesome!

[Nadrieril]

Good point! I'll look into fixing that

[Nadrieril]

Done! This is released in v1.1.0