Documentation site lacks version selection

Location (URL)

https://doc.rust-lang.org/std/

Summary

While reviewing documentation, after sometime away from Rust, I was surprise that the documentation site at https://doc.rust-lang.org/std/ did not provide a convenient means of selecting the Rust version for the documentation it provided. It did help display the Rust version of the documentation it was actually showing but a way to switch to an earlier version that was needed would have been nice. According to Google Gemini, I have to manually modify the URL to insert the correct Rust version, presumably in the correct format whatever that would be.

Start at the documentation site URL https://doc.rust-lang.org/std/ and investigate how Rust documentation versions are published and addressed. Determine where version selection could be exposed; done means users can conveniently switch from the displayed documentation to an earlier Rust version.