Updated Pterodactyl egg

I have reworked my previous Pterodactyl egg for Beam-MP.
The new egg does not require a locally-built docker image, making setup much easier.
Next to that, I also made sure that newly installed servers are always on the latest version, instead of always installing one hardcoded version.
You can find the egg here: https://github.com/VanishedMC/Pterodactyl-BeampMP-Egg