Add a way to browse the code where a lint is suppressed

[dtolnay]

Rendering an html page per lint, with links to docs.rs's code browser, would be sufficient I think.

We can show a few lines as a preview (similar to grep.app) and then link to e.g. https://docs.rs/crate/crossbeam-channel/0.5.1/source/src/err.rs#:~:text=clippy::trivially_copy_pass_by_ref for the full code.