Add milestones link

Author: ericholscher

docs/gsoc.rst

@@ -150,9 +150,11 @@ Additional Ideas
 
 We have some medium sized projects sketched out in our issue tracker with the tag *Feature Overview*.
 Looking through `these issues`_ is a good place to start.
-You can also look through any additional open issue to get ideas or what to work on.
+You might also look through our `milestones`_ on GitHub,
+which provide outlines on the larger tasks that we're hoping to accomplish.
 
 .. _these issues: https://github.com/rtfd/readthedocs.org/issues?direction=desc&labels=Feature+Overview&page=1&sort=updated&state=open
+.. _milestones: https://github.com/rtfd/readthedocs.org/milestones
 
 Possible Mentors
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