feat(binding): add AsyncPlugin as entry point for Async library

Introduces AsyncPlugin to serve as a standalone library-plugin entry point for the Async library. This allows other plugins to depend on Async without bundling it directly. The plugin installs a disconnect hook on start and ensures proper shutdown of tracked scopes.

binding/src/main/kotlin/com/mythlane/async/binding/AsyncPlugin.kt

@@ -0,0 +1,23 @@
+package com.mythlane.async.binding
+
+import com.hypixel.hytale.server.core.plugin.JavaPlugin
+import com.hypixel.hytale.server.core.plugin.JavaPluginInit
+import com.mythlane.async.Async
+
+/**
+ * Standalone library-plugin entry point. Drop the shaded jar in `mods/` and
+ * other plugins can depend on Async without bundling it themselves.
+ *
+ * Installs the disconnect hook on start and drains every tracked scope on
+ * shutdown. Plugins that bundle Async directly should keep calling
+ * [installAsync] and [Async.shutdown] themselves and not rely on this class.
+ */
+class AsyncPlugin(init: JavaPluginInit) : JavaPlugin(init) {
+    override fun start() {
+        installAsync()
+    }
+
+    override fun shutdown() {
+        Async.shutdown()
+    }
+}