Migrate to new Hytale plugin template structure

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.

src/main/java/org/example/plugin/ExamplePlugin.java

@@ -0,0 +1,27 @@
+package org.example.plugin;
+
+import com.hypixel.hytale.logger.HytaleLogger;
+import com.hypixel.hytale.server.core.plugin.JavaPlugin;
+import com.hypixel.hytale.server.core.plugin.JavaPluginInit;
+
+import javax.annotation.Nonnull;
+
+/**
+ * This class serves as the entrypoint for your plugin. Use the setup method to register into game registries or add
+ * event listeners.
+ */
+public class ExamplePlugin extends JavaPlugin {
+
+    private static final HytaleLogger LOGGER = HytaleLogger.forEnclosingClass();
+
+    public ExamplePlugin(@Nonnull JavaPluginInit init) {
+        super(init);
+        LOGGER.atInfo().log("Hello from " + this.getName() + " version " + this.getManifest().getVersion().toString());
+    }
+
+    @Override
+    protected void setup() {
+        LOGGER.atInfo().log("Setting up plugin " + this.getName());
+        this.getCommandRegistry().registerCommand(new ExampleCommand(this.getName(), this.getManifest().getVersion().toString()));
+    }
+}