Add Apex implementation

[berehovskyi]

Hi!

I've implemented hashids in Apex (a Java/C# like language used by Salesforce) : Github Repo This PR updates the hashids' website to add an Apex entry. All test cases are covered based on C#/Java ports test cases and the inputs and outputs are matched. Apex is a language similar to Java and in C#, it will not be difficult to review the source code. So please take a look.

Thanks!