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.

LibGUI/GTableView.h

@@ -1,9 +1,9 @@
 #pragma once
 
-#include <LibGUI/GModel.h>
-#include <LibGUI/GAbstractView.h>
 #include <AK/Function.h>
 #include <AK/HashMap.h>
+#include <LibGUI/GAbstractView.h>
+#include <LibGUI/GModel.h>
 
 class GScrollBar;
 class Painter;