Add wiki updating to publish steps

Author: oli-obk

PUBLISH.md

@@ -12,3 +12,9 @@ Steps to publish a new clippy version
 - `git pull`.
 - `git tag -s v0.0.X -m "v0.0.X"`.
 - `git push --tags`.
+- `git clone [email protected]:Manishearth/rust-clippy.wiki.git ../rust-clippy.wiki.git`
+- `./util/update_wiki.py`
+- `cd ../rust-clippy.wiki.git`
+- `git add *`
+- `git commit`
+- `git push`