Add custom Gamerules when creating worlds for Minecraft servers.

Create a level-gamerules.txt file when starting the Minecraft server, containing the following content:

I'll just give an example of how to write the level-gamerules.txt file for the Java Edition. It looks like this:

#Minecraft Level Gamerules
#Time
allowEnteringNetherUsingPortals=true
allowFireTickAwayFromPlayer=true
#And more...

It is called the next time a new world is created for the Minecraft server.

Its settings such as `Anygamerules=true` or `false` and `Numbergamerules=65535` are entirely consistent with Minecraft's default world rules.