Searching "&" and "&mut" in stdlib api docs should show "reference (primitive)"

[Havvy]

If you don't recall or know the name of the reference primitive (like, uh, I did earlier), searching on https://doc.rust-lang.org/std/ for "&", "&m", "&mu", and "&mut" should show the result "reference (primitive)" as the first result.

Likewise for [] and [;] for slices and arrays, and () and (,) and (,,) and etc. for tuples. And probably others.

[GuillaumeGomez]

Like said on IRC, it'll be complicated and we'll require a strong and huge update of the search functionalities.