Warn against here-links in doc comments

What it does

Warns when a user writes [here], [click here], [link] or [this link] in a doc comment. This lint would be in the “Style” category, as I think it is fairly universally agreed-upon that such links should be avoided (I have not seen arguments to the contrary, at least).

Advantage

Links of this form are widely considered bad for accessibility[1][2][3], among other reasons. It is recommended to change the link text to a short description of what is at the URL instead.

Drawbacks

Sometimes it is non-obvious how to rewrite a here-link into the preferred form, which could increase friction when writing docs.

Example

/// For more details on this function, click [here](crate).

Could be written as:

/// For more details on this function, see [the crate-level docs](crate).

The issue does not name an implementation file or test. Start by locating Clippy's existing documentation-comment style lints and their tests, then determine where the proposed patterns should be recognized. Done means the Style lint warns for the four listed link texts and has coverage for the examples, while allowing descriptive link text.