Include the issue number in what's new

Camilo Cota · Camilo Cota · commit 1472d80bccd2 · 2016-05-16T18:53:15.000+02:00
diff --git a/doc/source/whatsnew/v0.18.2.txt b/doc/source/whatsnew/v0.18.2.txt
@@ -38,7 +38,7 @@ Other enhancements
      idx = pd.Index(["a1a2", "b1", "c1"])
      idx.str.extractall("[ab](?P<digit>\d)")
 
-- Support decimal option in PythonParser
+- Support decimal option in PythonParser (:issue:`12933`)
 
 .. _whatsnew_0182.api:
 
