Update to Minecraft 1.21.8

Add PlaceholderAPI placeholders for shop and vote

Closes Azuriom#16 and closes Azuriom#54

Fix FileAlreadyExistsException after server upgrade (fixes Azuriom#50)

Fix build

Prevent remapping on Paper 1.20.6/1.21

Correctly handle HTTP redirects & async SkinsRestorer requests

Closes Azuriom#40

Refactor tests & universal SkinsRestorer integration

Closes Azuriom#34 and closes Azuriom#35

Update users API & support SkinRestorer v15

Closes Azuriom#32

Manually download netty-codec-http when missing (fixes Azuriom#29)

AuthMe, SkinRestorer & LimboAuth integrations

Closes Azuriom#17, closes Azuriom#24 and closes Azuriom#26