1.13 is one of the most complicated updates we've had, consider supporting the project and helping us continue. Also report bugs here. Huge thanks to creeper123123321, Matsv, Pokechu22 and the Hive for helping us release today (without any of them it would not be possible).
Known bugs:

• Blocks which connect do not connect properly (fences, doors, stairs etc) - Click here to follow progress on GitHub. Due to connections now being serverside we're looking for help in developing an optimal solution.
• Biomes are not correctly registered (this is an issue we are urgently looking into and will issue an update for soon)
• Falling block particles at your feet may be bugged (also looking into these)

Changelog:

• 1.13 client support (by @creeper123123321, @Matsv, @pokechu22, @PureGero and myself)
• Fix locale bugs (by @pokechu22)
• Fix bugs with book formatting (by @mmxw11)
• Config option for new quick move patch(by @mmxw11)
• Fix achievements being broadcasted when blank to 1.12+
• Fix issues with ProtocolDetection on bungee sometimes throwing NPEs
• Fix tab complete on Sponge (by @creeper123123321)
• Fix /viaversion dump (GitHub no longer supports anonymous gists)
• Fix issue with running sync tasks (by @Matsv)
• Fix internal server support on Sponge (by @creeper123123321)

Huge thanks to all the awesome people contributing code to us (listed above), the team has spent 100s of hours on this update <3

(This update was posted while I was on holiday, bug fixes/version releases may take a few days, contributing & helping us fix bugs is appreciated)