Update README.md

Timers/README.md

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 This chapter describes timers and time management related concepts in the linux kernel.
 
 * [Introduction](http://0xax.gitbooks.io/linux-insides/content/Timers/timers-1.html) - this part is introduction to the timers in the Linux kernel.
+* [Introduction to the clocksource framework](https://github.com/0xAX/linux-insides/blob/master/Timers/timers-2.md) - this part describes `clocksource` framework in the Linux kernel.