Start Timing Attacks section with a definition, use cryptography as an example

[sam-ellis]

The Timing Attacks section launches straight in with cryptography as a place where timing attacks are used, possibly leading to the conclusion that cryptography is the only place where timing attacks occur. I would recommend to re-write the first paragraph to define Timing Attacks abstractly first, then use cryptography as an example of where this can occur.

[kbeyls]

Thank you, I think this is a very good suggestion!

[kbeyls]

@allcontributors please add @sam-ellis for bug, ideas, review

[allcontributors[bot]]

@kbeyls

I've put up a pull request to add @sam-ellis! :tada: