Fix for the Minecraft FTB Egg

[MaxPtg]

Description

The FTB API has changed and as such, the current egg does not work correctly. I have done the following to fix this:

• Improve the startup script to be more robust and implemented better error handling
• Change the startup command to work with the new neoforge versions
• Update the README with examples on how to fill the variables within the Panel

I am aware that there already is a PR that is supposed to fix this but it didn't work for me without additional changes and it seems to be abandoned. As a result, I tried fixing it myself.

This updated Egg has been tested with the following modpacks on Pelican + Pterodactyl:

• FTB Evolution (IDs & Name+Version-String)
• FTB Revelation (IDs & Name+Version-String)
• FTB Skies (IDs & Name+Version-String)
• FTB Skies 2 (IDs & Name+Version-String)

I am not sure about the Log4J fixes. Some of the older modpacks with older Java versions still download the Log4J fix jar but the new ones do not. The problem is that if the jar is not downloaded (on newer packs), the startup command won't work correctly. Not sure how to handle this. I'd suggest a startup script that checks if the jar exists and adjusts the startup command accordingly.

Checklist for all submissions

• [x] Have you followed the guidelines in our Contributing document?
• [ ] Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• [x] Have you tested and reviewed your changes with confidence that everything works?
• [x] Did you branch your changes and PR from that branch and not from your master branch?
  • If not, why?:

• [x] You verify that the start command applied does not use a shell script
  • [x] If some script is needed then it is part of a current yolk or a PR to add one
• [x] The egg was exported from the panel