Update files stored locally when they are different from .jar files

[LouissXI]

When switching my Limbo server from the 1.18 version to the 1.19 version, an error appeared telling me that it could not find the PacketPlayOutSpawnEntityLiving class. After a few tries I realized that it was because the mappings.json file stored locally was not updated. To avoid this kind of error, I made this fix to solve the problem by simply updating the mappings.json file and dimension_registry.json if the locally stored ones are different from the ones contained in the .jar.

[LOOHP]

I feel like it is better to update the mappings.json when limbo is upgraded, instead of every time it is different.

[LouissXI]

Sure no problem