Fix open QML file when the kate QML highlighter file are installed

Apparently creator uses the kate highlighter file to find the
mumetype of a file.
But kate annotate qml file with text/x-qml instead of application/x-qml
that we expect

src/plugins/qmljseditor/QmlJSEditor.mimetypes.xml

 <?xml version="1.0"?>
 <mime-info xmlns='http://www.freedesktop.org/standards/shared-mime-info'>
     <mime-type type="application/x-qml">
+        <alias type="text/x-qml"/>
         <sub-class-of type="text/plain"/>
         <comment>QML file</comment>
         <glob pattern="*.qml"/>