Add changes file for Qt 5.12.3

+ fea4d302 Gstreamer: Set surface from renderer before creating pipeline
+ 09490d1a Doc: Fix documented QtMultimedia import
+ 935967a4 Fix compile failure with gstreamer 0.10
+ d665520e Bump version
+ 226f802f Add source url to 'decoding error' warning
+ c296df78 Fix QCameraInfo to be invalid if camera failed to find device
+ 80411380 winrt: Use highest supported resolution for camera preview/image capture
+ f4181938

 Android: Use CaptureStillImage as default capture mode

Change-Id: I2cf7a9c86b08e72ffbea9901371a40610b65eadd
Reviewed-by: Christian Strømme <christian.stromme@qt.io>

dist/changes-5.12.3

+Qt 5.12.3 is a bug-fix release. It maintains both forward and backward
+compatibility (source and binary) with Qt 5.12.0 through 5.12.2.
+
+For more details, refer to the online documentation included in this
+distribution. The documentation is also available online:
+
+https://doc.qt.io/qt-5/index.html
+
+The Qt version 5.12 series is binary compatible with the 5.11.x series.
+Applications compiled for 5.11 will continue to run with 5.12.
+
+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.
+
+ - This release contains only minor code improvements.
+
+****************************************************************************
+*                            Qt 5.12.3 Changes                             *
+****************************************************************************
+
+- Fixed QCameraInfo to be invalid if camera failed to find device.
+
+****************************************************************************
+*                      Platform Specific Changes                           *
+****************************************************************************
+
+Gstreamer
+---------
+
+ - [QTBUG-73557] Fixed setting surface from current renderer after changing the pipeline.
+
+ WinRT
+ -----
+
+  - [QTBUG-72874] Fixed camera preview/image capture to use highest supported resolution.