website: make lint categories linkable

[matthiaskrgr]

https://rust-lang-nursery.github.io/rust-clippy/master/index.html

It would be cool to be able to set a link to preselected lint groups like "Perf", maybe something like https://rust-lang-nursery.github.io/rust-clippy/master/index.html?sel=perf and have only the perf lints show up when clicking the link (perf checkbox would be marked).

Once this is done, we can set urls to the respective lint groups in the README.md where all the lint groups are listed. :)

[phansch]

If someone wants to get started on this, the code to touch would be in util/gh-pages/index.html.
The website uses Angular 1.4.12 currently, so the handling of the URL parameters would have to happen at the bottom of the file in the lintList controller, similar to how the lint deeplink is implemented:
https://github.com/rust-lang-nursery/rust-clippy/blob/97840090b78ce1f370c3380e8a703da420fe3a98/util/gh-pages/index.html#L209-L212