[Docs] Add vpscheap.net as a tested VPS provider

Hi, I recently tested the script with my KVM VPS from vpscheap.net with Debian (1GB of RAM, 1 core and 20GB of storage) and it worked awesomely! (the first time it didn't, however, but in the second everything went smooth. Then I migrated Hyperbola GNU/Linux-libre [Arch-based], but that's another story), so I wanted to request its addition to the documentation (because in the README.md you ask users to do 😝 )

P.S.: I would add a note in the README.md about the type of VPS's virtualization where it works. I previously tried in a OpenVZ one and it didn't work (of course).