Doc: Updated change log with documentation entry

Change-Id: I1cd4dc70265f2425045328910be12a0cfaeb795c
Reviewed-by: Sergio Ahumada <sergio.ahumada@digia.com>

dist/changes-5.0.1

@@ -28,6 +28,7 @@ General Improvements
  - qmltest: Added the possibility to use QApplication
  - [QTBUG-28611] Quick tests: Introduce QQmlMessageHandler.
  - Compile with QT_NO_WHEELEVENT.
+ - Various documentation improvements.
 
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