Update README.md (#12)

Bump the pre-commit recommended version number to be a bit more recent.
diff --git a/README.md b/README.md
index 21ffbaf..a01b6df 100644
--- a/README.md
+++ b/README.md
@@ -71,7 +71,7 @@
 
 ```yaml
 - repo: https://github.com/google/keep-sorted
-  rev: v0.1.0
+  rev: v0.2.0
   hooks:
     - id: keep-sorted
 ```