Update README.md

Author: Widdershin

README.md

@@ -33,6 +33,7 @@ Notes from my research for forest-lang, mostly in the form of links to reference
 * [Simple explanation of type unification](https://eli.thegreenplace.net/2018/unification/)
 * [Jan's proposal to add Row Types to GHC](https://github.com/ghc-proposals/ghc-proposals/pull/180)
 * [Type driven development in Idris](https://www.youtube.com/watch?v=mOtKD7ml0NU&feature=youtu.be)
+* [A reckless introduction to Hindley-Milner type inference](http://reasonableapproximation.net/2019/05/05/hindley-milner.html)
 
 ### Proofs