add write a kernel in C

Author: tuvtran

README.md

@@ -43,6 +43,7 @@ To get started, simply fork this repo. Please refer to [CONTRIBUTING.md](CONTRIB
 * [Build a Live Code-reloader Library for C++](http://howistart.org/posts/cpp/1/index.html)
 * [Write a hash table in C](https://github.com/jamesroutley/write-a-hash-table)
 * [Let's Build a Simple Database](https://cstack.github.io/db_tutorial/)
+* [Let's Write a Kernel](http://arjunsreedharan.org/post/82710718100/kernel-101-lets-write-a-kernel)
 
 ## C#: