README: Make the wiki links more useful.

The page we want them to find is 'getting started developing'.

README.md

@@ -86,8 +86,9 @@ supported build environments that are most likely to work.
 Rust currently needs about 1.5 GiB of RAM to build without swapping; if it hits
 swap, it will take a very long time to build.
 
-There is a lot more documentation in the [wiki].
+There is more advice about [hacking on Rust][hack] on the [wiki].
 
+[hack]: https://github.com/rust-lang/rust/wiki/Note-getting-started-developing-Rust
 [wiki]: https://github.com/rust-lang/rust/wiki
 
 ## Getting help