Add clang-format file

Also run it across the whole tree to get everything using the One True Style.
We don't yet run this in an automated fashion as it's a little slow, but
there is a snippet to do so in makeall.sh.

Applications/Taskbar/TaskbarButton.h

@@ -1,7 +1,7 @@
 #pragma once
 
-#include <LibGUI/GButton.h>
 #include "WindowIdentifier.h"
+#include <LibGUI/GButton.h>
 
 class TaskbarButton final : public GButton {
 public:

Applications/Taskbar/TaskbarWindow.h

@@ -1,6 +1,6 @@
-#include <LibGUI/GWindow.h>
-#include <LibGUI/GWidget.h>
 #include "WindowList.h"
+#include <LibGUI/GWidget.h>
+#include <LibGUI/GWindow.h>
 
 class TaskbarWindow final : public GWindow {
 public:

Applications/Taskbar/WindowIdentifier.h

@@ -18,6 +18,7 @@ public:
     {
         return m_client_id == other.m_client_id && m_window_id == other.m_window_id;
     }
+
 private:
     int m_client_id { -1 };
     int m_window_id { -1 };

Applications/Taskbar/WindowList.h

@@ -1,10 +1,10 @@
 #pragma once
 
+#include "WindowIdentifier.h"
 #include <AK/AKString.h>
 #include <AK/HashMap.h>
-#include <SharedGraphics/Rect.h>
 #include <LibGUI/GButton.h>
-#include "WindowIdentifier.h"
+#include <SharedGraphics/Rect.h>
 
 class Window {
 public:
@@ -64,7 +64,8 @@ class WindowList {
 public:
     static WindowList& the();
 
-    template<typename Callback> void for_each_window(Callback callback)
+    template<typename Callback>
+    void for_each_window(Callback callback)
     {
         for (auto& it : m_windows)
             callback(*it.value);