Fabric Shield Lib 1.4.0-pre1 for Minecraft 1.17.1

This is a complete rewrite of the Fabric Shield Library.

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• ShieldEvent isn't a thing anymore. Now using Fabric Events. Fix #21
• FSL still provides a basic shield class but it is implemented using interfaces. Fix #27
• Mixins shouldn't have conflicts anymore. Fix #25
• LIbrary was simplified so hopefully less strange behavior should happen in edge cases. Fix #18 #17

Future Plans

Full banner support using a premade FabricBannerShield class.