Add MSRV to readme

[Stargateur]

I think that good to put MSRV in the README.

Fix somehow https://github.com/matklad/once_cell/issues/201

[matklad]

I think this is already sufficiently documented in

• https://github.com/matklad/once_cell/blob/3cd65494663f003b9b2e0be5b37b3426e543f72a/src/lib.rs#L276-L282 and
• https://github.com/matklad/once_cell/blob/3cd65494663f003b9b2e0be5b37b3426e543f72a/Cargo.toml#L7

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