Support for horizontal scroll

[nikita-tomilov]

Hello!

Have you considered adding a support for emulating horizontal scroll, or this is not needed for vast majority of this library's users?

It seems that this is possible to add such functionality in a painless way: https://arduino.stackexchange.com/questions/46055/can-the-mouse-library-scroll-horizontally

I had made a fork of this lib with the aforementioned adjustments (https://github.com/nikita-tomilov/HMouse), and it actually works as expected, but I had to rename the class because of conflict with another library. I will be more than happy to create a proper pull request to this repository (without such renaming), if there is any need in this.