Taskbar+WindowServer: Adding to Quick Launch via windows :^)

You can now add applications to Quick Launch via the context
menu option of their windows. Clicking it creates an event with the
stored PID of the process that created the window. The Taskbar receives
the event and tells the QuickLaunchWidget to add the PID, which then
gets the executable using /sys/kernel/processes. It also looks for an
AppFile using the name from the process object and if there is one, it
uses that, since it should contain a better formatted name.

Userland/Libraries/LibGUI/Event.h

@@ -1,6 +1,7 @@
 /*
  * Copyright (c) 2018-2023, Andreas Kling <kling@serenityos.org>
  * Copyright (c) 2022, the SerenityOS developers.
+ * Copyright (c) 2023, David Ganz <david.g.ganz@gmail.com>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -73,6 +74,7 @@ public:
         WM_SuperDigitKeyPressed,
         WM_WorkspaceChanged,
         WM_KeymapChanged,
+        WM_AddToQuickLaunch,
         __End_WM_Events,
     };
 
@@ -264,6 +266,20 @@ private:
     const DeprecatedString m_keymap;
 };
 
+class WMAddToQuickLaunchEvent : public WMEvent {
+public:
+    explicit WMAddToQuickLaunchEvent(int client_id, pid_t pid)
+        : WMEvent(Event::Type::WM_AddToQuickLaunch, client_id, 0)
+        , m_pid(pid)
+    {
+    }
+
+    pid_t pid() const { return m_pid; }
+
+private:
+    pid_t m_pid;
+};
+
 class MultiPaintEvent final : public Event {
 public:
     explicit MultiPaintEvent(Vector<Gfx::IntRect, 32> rects, Gfx::IntSize window_size)