Added the documentation for the 'use' keyword

[poliorcetics]

This is a partial fix of #34601.

I heavily inspired myself from the Reference on the use keyword.

I checked the links when compiling the documentation, they should be ok.

I also added an example for the wildcard * in the case of types, because it's behaviour is not import everything like one might think at first.

[rust-highfive]

r? @LukasKalbertodt

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[poliorcetics]

@lcnr Since _ is for traits only, should I add an example for that too or is the line about it clear enough ?

[lcnr]

I think an example would be helpful here, but as this feature is very rarely used, a link to
https://doc.rust-lang.org/stable/reference/items/use-declarations.html?highlight=use#underscore-imports might be better.

[poliorcetics]

I think an example would be helpful here, but as this feature is very rarely used, a link to
https://doc.rust-lang.org/stable/reference/items/use-declarations.html?highlight=use#underscore-imports might be better.

There is a link to this page already (though not the exact section), the one named as [Reference], should repeat it once more (with the exact section) or is okay with what's already here ?

[lcnr]

Seems good to me 👍

[Dylan-DPC-zz]

r? @Dylan-DPC

@bors r+ rollup

[bors]

📌 Commit 4bae9e5 has been approved by Dylan-DPC