Mark error fabric's mod initializer if it doesn't implements their specified common interfaces

[KisaragiEffective]

In Fabric, we need to make mod initializer implements their interfaces [1]. one of example is:

@net.fabricmc.api.Environment(net.fabricmc.api.EnvType.CLIENT)
public class MyMod implements ClientModInitializer { // <--- needs ClientModInitializer
}

If MyMod doesn't implement it [1], ClassCastException will be thrown.

I would like to notice about that before run games, as well.

[1]: ModInitializer, ClientModInitializer, and ServerModInitializer

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[KisaragiEffective]

no, please review this

[KisaragiEffective]

bump