message: link to crater bot docs
diff: @@ -100,6 +100,8 @@ regressions in the Rust compiler, and it does this by building large number of
  crates, running their test suites and comparing the results between two
  versions of the Rust compiler.
  +Crates comes with a [bot to trigger experiments](https://github.com/rust-lang/crater/blob/master/docs/bot-usage.md).
  +
  ## docs.rs
  [docs.rs](https://docs.rs/) builds and serves the rustdoc documentation for
  