message: book: add edit links to specific pages
diff: @@ -4,3 +4,4 @@ author = "Alex Crichton, Steve Klabnik and Carol Nichols, with Contributions fro
  [output.html]
  git-repository-url = "https://github.com/rust-lang/cargo/tree/master/src/doc/src"
  +edit-url-template = "https://github.com/rust-lang/cargo/edit/master/src/doc/{path}"
  