Update 'mathematics.md'

mathematics.md

@@ -52,6 +52,7 @@
 - [MIP\* = RE Henry Yuen Talk](https://cacm.acm.org/magazines/2021/11/256404-mip-re/fulltext)
 - [Bertrand Paradox](https://en.wikipedia.org/wiki/Bertrand_paradox_(probability))
 - [Weierstrass function](https://en.wikipedia.org/wiki/Weierstrass_function)     
+- [Turing Category](https://ncatlab.org/nlab/show/Turing+category)
 
 
 #### Tables