Add a lint list, to display the documentation for installed lints

[xFrednet]

Lints often have more context and reasoning than what's included in the emitted diagnostic message. Rustc and Clippy both provide an external list of the lints with a detailed explanation and suggestions how to fix the problem:

1. https://rust-lang.github.io/rust-clippy/master/index.html
2. https://doc.rust-lang.org/rustc/lints/listing/warn-by-default.html

Marker should also provide an option to display which lints are installed, along with the documentation provided by them in the declare_lint! macro. This could be in the form of a cargo marker doc comment, that fetches the description from the lint crates and then combines them into a website. Ideally searchable, and more than just plain HTML.