docs: fix link to the email project. #44

Author: nedbat

README.rst

@@ -184,7 +184,8 @@ The `sample digest <sample_>`_ is published daily using a GitHub Action from
 its own repo: `nedbat/dinghy_sample <sample_repo_>`_.  You can use it as a
 starting point for your own publishing.
 
-There's also a `separate project <email_project>`_ which sends a daily email of GitHub activity.
+There's also a `separate project <email_project_>`_ which sends a daily email
+of GitHub activity.
 
 
 .. _sample: https://nedbat.github.io/dinghy_sample/3day.html