Migrate the project from Gradle Kotlin DSL to Groovy DSL: update README to reference build.gradle/settings.gradle and change code blocks to Groovy. Remove build.gradle.kts. Add runServerJar and runServer tasks in build.gradle that depend on shadowJar and launch the Hytale server (uses hytaleHome paths, assets, and optional user mods). Bump plugin manifest version to 0.0.3 and set a concrete ServerVersion string. Fixed some issues.
Replaces the previous Kotlin-based Gradle build and template files with a new Java-based Gradle build system and updated example plugin code. Removes old build scripts, plugin template, and configuration, and introduces a new ExamplePlugin with updated manifest, command, and recipe example. Updates documentation and project configuration to match the new structure and usage.
