Docs: avoid using "here" as link text on docs index page

[damag]

This is a minor issue but I'd suggest not using "here" as the link text for the standard library docs on the documention index page. Having informative link text makes the link easier to find and is generally considered best practice.

Maybe just link on "standard library" and drop the word "here"? i.e.:

You can find function-level documentation for the entire standard library.

[liigo]

You can find function-level documentation for the entire standard library (std).

and add the crate name std?