BuildNotifier

• Removed Waterfall support as it's EOL.
• Removed Folia support due to Paper not releasing public versions.
• Fixed support for Velocity 3.4.0 (#18).
• Updated to Java 21.
• Added bStats.
• Added update checker for the plugin itself.

• Fixed all related Folia issues.
• Removed all references to the old name.
• Make all requests async.

• Added Folia support. This will only work when Paper releases public builds.
• Fixed Paper plugin's permission node being incorrect.
• Fixed Velocity plugin's event not being registered.

First release of plugin.