General egg cleanup & fixes

[TASelwyn]

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This pull request contains the following changes as general improvements/ease of use of the egg repository.

• General cleanup
• Fixes unturned/unturned (removes duplicate)
• Fixes egg url to minecraft/java/feather, previously was 404'ing due to bad url
• Adds readme for Tuinity/Nukkit (now abandoned)/PocketMine MP
• Adds abandoned warning on Nukkit, where NukkitX is the replacement.
• Moves GeyserMC into cross_platform for minecraft/java/proxy as it's not just for bedrock.
• Removes DragonProxy in place of a "deprecated/abandoned" warning (Use GeyserMC now)
• Updates /proxy/cross_platform to now have GeyserMC
• Removes Bedrock proxy folder as there's nothing inside.