Add MSRV to readme

[Stargateur]

I think that good to put MSRV in the README.

Fix somehow #201

[matklad]

I think this is already sufficiently documented in

• once_cell/src/lib.rs

  Lines 276 to 282 in 3cd6549

  	//! # Minimum Supported `rustc` Version
  	//!
  	//! If only the `std` feature is enabled, MSRV will be updated conservatively,
  	//! supporting at least latest 8 versions of the compiler. When using other
  	//! features, like `parking_lot`, MSRV might be updated more frequently, up to
  	//! the latest stable. In both cases, increasing MSRV is *not* considered a
  	//! semver-breaking change.

  and

• once_cell/Cargo.toml

  Line 7 in 3cd6549

  rust-version = "1.60"

This extra information is very useful for users who want to learn the context about a specific policy, but I don't think it's useful enough for enough of people to spend valuable README.md space on that.

[Stargateur]

The only problem of putting it in the code is that user need to look rust documentation, I generally include the readme in the documentation crate level. Maybe you will be interested to include the readme in crate documentation ?

This extra information is very useful for users who want to learn the context about a specific policy, but I don't think it's useful enough for enough of people to spend valuable README.md space on that.

Feel free to close, it's your project haha ^^ was just an idea

[matklad]

Yeah, the duplication between lib.rs and readme is unfortunate, but I hold lib.rs as the source of truth, and try to avoid using readme for anything. We used to duplicate the docs between readme and lib.rs, but then pared that down.

[Stargateur]

I generally use that #![doc = include_str!("../readme.md")] but I don't have your experience yet haha