Added changelog for QtDoc

Change-Id: I8e46b898e7938a79d5cb24f832f7a7787591f813
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>

dist/changes-5.7.0

@@ -0,0 +1,25 @@
+Qt 5.7 introduces many new features and improvements along with bug fixes
+over the 5.6.x series. For more details, refer to the documentation
+included in this distribution. The documentation is also available online:
+
+  https://doc.qt.io/qt-5/
+
+The Qt version 5.7 series is binary compatible with the 5.6.x series.
+Applications compiled for 5.6 will continue to run with 5.7.
+
+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.
+
+****************************************************************************
+*                           General                                        *
+****************************************************************************
+  - Improved Qt for embedded Linux documentation.
+  - Added documentation on Android Services.
+  - Updated Qt licensing information.
+  - Added documentation on Clang compiler under Windows.
+  - Fixed several instances of missing, incorrect, or obsolete information.