Aktualisiere README, um aktuelle API und Funktionen zu reflektieren

Die README wurde aktualisiert, um die Projektidentität als eigenständige Weiterentwicklung zu verdeutlichen. Sie dokumentiert nun auch die jüngsten API-Erweiterungen wie Linksklick-Callbacks und verbesserte UTF-8-Unterstützung unter Windows, sowie relevante interne Felder.

README.md

@@ -16,13 +16,17 @@ Works well on:
 
 The code is C++ friendly and will compile fine in C++98 and up.
 
-This fork is intended to bring together the [original work of Serge Zaitsev](https://github.com/zserge/tray) and the most interesting forks and PRs of respectable contributors:
+This repository started as a fork of the [original work by Serge Zaitsev](https://github.com/zserge/tray), but it is now maintained as a separate continuation. It keeps the small public C API and cross-platform focus, while carrying its own fixes and behavior changes.
 
-* [Only process messages coming from the tray window on Windows](https://github.com/zserge/tray/pull/18)
-* [Become C++-friendly](https://github.com/zserge/tray/pull/16)
-* [Fix all menu items have a check box](https://github.com/zserge/tray/pull/11)
-* [Add support for tooltip](https://github.com/zserge/tray/pull/11)
-* Darwin implementation translated from C to Objective C adapted from [@trevex fork](https://github.com/trevex/tray)
+Compared to the original upstream, this fork already includes and continues work around:
+
+* improved Windows message handling
+* C++-friendly headers and usage
+* tooltip support
+* checkbox/menu state fixes
+* Darwin/AppKit support adapted from the [@trevex fork](https://github.com/trevex/tray)
+* support for left-click callbacks
+* Windows UTF-8 tray text handling
 
 ## Prerequisites
 
@@ -63,6 +67,10 @@ struct tray {
   const char *icon;
   char *tooltip;
   struct tray_menu *menu;
+  void *icon_handle;
+  int icon_is_shared;
+  void (*left_click_cb)(void *context);
+  void *left_click_context;
 };
 
 struct tray_menu {
@@ -91,6 +99,8 @@ array must have `text == NULL`.
 ### Notes
 
 * `tooltip` is optional.
+* `left_click_cb` and `left_click_context` are optional.
+* `icon_handle` and `icon_is_shared` are backend-specific fields used internally by the Windows implementation and should usually be left untouched by callers.
 * A separator is created by using `text = "-"`.
 * Some behavior may depend on the underlying backend or desktop environment.
   Keep the public API generic and treat platform-specific interaction details as