doc/guide/dependencies: Add a 'rust' language marker
authorW. Trevor King <wking@tremily.us>
Mon, 8 Jan 2018 21:56:54 +0000 (13:56 -0800)
committerW. Trevor King <wking@tremily.us>
Mon, 8 Jan 2018 21:56:54 +0000 (13:56 -0800)
commit272227403d80f6dc1fba840566b1a7991b9e1a54
tree59fc6a78101e8224c45e10ad66a8fc0b4e926915
parentf60ece98c10aa3716d037524da4ee989e212fe19
doc/guide/dependencies: Add a 'rust' language marker

This had been added to the non-book docs in 2ad45a56 ([doc] Sync back
doc/book changes into old docs, 2017-08-31, #4455), despite the fact
that the book didn't actually have that marker:

  $ git cat-file -p 2ad45a56:src/doc/book/src/guide/dependencies.md | grep -A2 'You can now use the'
  You can now use the `regex` library using `extern crate` in `main.rs`.

  ```
src/doc/src/guide/dependencies.md