Adds compatibility with ViaVersion and ViaBackwards 5.11.0

Other changes

• Fixed custom sound handling in 1.9->1.8. (Thanks @Beaness)
• Improved newline chat message handling in 1.8->1.7. (Thanks @Beaness)
• Fixed potential teleport confirm desync in 1.8->1.7. (Thanks @Beaness)

Please also read the 4.1.2 changelog: https://github.com/ViaVersion/ViaRewind/releases/tag/4.1.2

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I'll continue improving this project to the best of my ability.