async-std deprecation message not sufficiently advertised

[harmic]

The recent deprecation message committed to this repo appears in the README and as a consequence on crates.io, but it does not appear:

• On the docs.rs landing page
• On the async.rs page (which is linked as the homepage on docs.rs)

Given the name of this package & the slick home page it is likely that people stumbling on one of the above two resources will think async-std is a semi-official crate and a good choice for a new project.

It could also be good to add #![deprecated(since="1.13.1",note="some message")] to the main lib.rs. That would result in deprecation warnings at compile time. Unfortunately you get one warning per reference to anything used from the crate - I would rather get a single warning to say the whole crate is deprecated, but I can't see any way to do that.

I also have some reservations about a blanket recommendation to switch to smol. While I am sure that smol is great, the fact is that tokio is far more widely used & supported, and like it or not is the defacto standard async runtime. It would be fairer to developers who are faced with the need to switch runtimes to at least list the main alternatives.