Update project configuration and refactor codebase

- Migrated Minestom dependency to new groupId.
- Added Maven Shade plugin for packaging.
- Switched Java version to 21 and corrected JDK settings.
- Refactored terrain generation logic to use the updated Minestom API.
- Replaced deprecated particle creation methods.
- Enabled Velocity proxy support.
- Updated various configuration files to align with the new build setup.

target/maven-archiver/pom.properties

@@ -0,0 +1,5 @@
+#Generated by Maven
+#Fri Dec 19 20:45:21 CET 2025
+artifactId=EndlessJumper
+groupId=org.example
+version=1.0-SNAPSHOT