base: Add link to "A reflection on types"

Fixes #17181.

libraries/base/Type/Reflection.hs

@@ -18,6 +18,7 @@
 -- * Simon Peyton-Jones, Stephanie Weirich, Richard Eisenberg,
 -- Dimitrios Vytiniotis. "A reflection on types."
 -- /Proc. Philip Wadler's 60th birthday Festschrift/, Edinburgh (April 2016).
+-- ([PDF](https://www.microsoft.com/en-us/research/wp-content/uploads/2016/08/dynamic.pdf))
 --
 -- The interface provides 'I.TypeRep', a type representation which can
 -- be safely decomposed and composed. See "Data.Dynamic" for an example of this.