Add changes file for 5.8.0

Change-Id: I6e9429e007d2adbfbd878662388759454339683d
Reviewed-by: Jani Heikkinen <jani.heikkinen@qt.io>

dist/changes-5.8.0

+Qt 5.8 introduces many new features and improvements as well as bugfixes
+over the 5.7.x series. For more details, refer to the online documentation
+included in this distribution. The documentation is also available online:
+
+  http://doc.qt.io/qt-5/index.html
+
+The Qt version 5.8 series is binary compatible with the 5.7.x series.
+Applications compiled for 5.7 will continue to run with 5.8.
+
+Some of the changes listed in this file include issue tracking numbers
+corresponding to tasks in the Qt Bug Tracker:
+
+  https://bugreports.qt.io/
+
+Each of these identifiers can be entered in the bug tracker to obtain more
+information about a particular change.
+
+****************************************************************************
+*                              New Features                                *
+****************************************************************************
+
+ - Added support for styles in any QML import path under the directory
+   QtQuick/VirtualKeyboard/Styles/<style>.
+ - Added API to support VKB selection handles.
+ - Added Romanian keyboard layout.
+ - Add new property InputContext.uppercase, which is set to
+   true when either InputContext.shift or InputContext.capsLock is true