Link README to the new contributor guide

Author: ehuss

README.md

@@ -4,18 +4,4 @@ This document is the primary reference for the Rust programming language.
 
 ## Contributor docs
 
-There are several pages for those working on the reference:
-
-* [Authoring guide](https://github.com/rust-lang/reference/blob/master/docs/authoring.md): Guidelines for writing content.
-* [Review policy](https://github.com/rust-lang/reference/blob/master/docs/review-policy.md): Guidelines for reviewers.
-* [Grammar](https://github.com/rust-lang/reference/blob/master/docs/grammar.md): How the grammar syntax works.
-* [Attribute template](https://github.com/rust-lang/reference/blob/master/docs/attribute-template.md): The standard template for documenting an attribute.
-
-## Running tests
-
-There are several different kinds of tests you can run (these are enforced on CI):
-
-* `mdbook test`: This will run the inline Rust codeblocks (internally it uses `rustdoc` to do this).
-* `cargo xtask style-check`: This will validate some style checks (see [authoring guide](docs/authoring.md)).
-* `cargo xtask linkcheck`: This will validate that markdown links aren't broken.
-* `cargo xtask test-all`: Runs all tests.
+See the [Contributor Guide](https://rust-lang.github.io/reference/contributor-guide/) for information on contributing to the Reference.