Added api testing library hikaku

[cc-jhr]

It didn't really fit in the categories under "Testing", so I created a new one "Validation". I hope that was okay.

[djhi]

I think it actually fit in the testing category. Can you move it there? Thanks

[cc-jhr]

I think it actually fit in the testing category. Can you move it there? Thanks

Done

[fzaninotto]

I'm not sure that we should put language-specific testing tools in "testing" - rather in their language section. I suggestion you move that link to the Java section. Sorry for the double move!

[cc-jhr]

So do you expect a language section under testing like Testing => Java? Because I wouldn't put it under Servers => Java since it's a testing library not a server.
With rest-assured you already have a language specific library in testing by the way. 😉