README needs correction for permissions

[TonyGravagno]

I appreciate the PR for the README regarding permissions. However, if we just update permissions.yml as documented now the following error results on server startup:

ERROR]: Permission in permissions.yml was already defined
java.lang.IllegalArgumentException: The permission eternallight.target is already defined!

I can look at this if required. Anyone else?

[Masstrix]

Honestly permissions have always been a bit funky and people seemed to struggle with them or they often broke with previous versions. It's quite possibly the way I implemented permissions in the plugin as I always used my own "permission" system for my personal plugins in the past.

Something to that can be looked into at some point.

[TonyGravagno]

Linking with #19