ModelShifter

This release of ModelShifter includes a lot of internal changes and adds a lot of new features to model rendering:

• Completely reworked the way features (held items, elytra, etc.) are handled internally
• Features now move with the model in animations
• Added held item and elytra features to some models which didn't have them before due to the features not moving with animations
• Added badges for supported features to the model selection screen
• Models now actually move correctly when flying with an elytra or swimming
• Re-added and fixed second skin layer on the baby model
• Added support for 1.21.3 and 1.21.4
• Added Norwegian language support by IgorYT