contrib: add qml in .gitignore

Fixes the following untracked files:

? contrib/qml/QML/plugins.qmltypes
? contrib/qml/QML/qmldir
? contrib/qml/QtCore/libqtqmlcoreplugin.a
? contrib/qml/QtCore/libqtqmlcoreplugin.prl
? contrib/qml/QtCore/plugins.qmltypes
? contrib/qml/QtCore/qmldir
? contrib/qml/QtQml/Models/libmodelsplugin.a
? contrib/qml/QtQml/Models/libmodelsplugin.prl
? contrib/qml/QtQml/Models/plugins.qmltypes
? contrib/qml/QtQml/Models/qmldir
? contrib/qml/QtQml/WorkerScript/libworkerscriptplugin.a
? contrib/qml/QtQml/WorkerScript/libworkerscriptplugin.prl
? contrib/qml/QtQml/WorkerScript/plugins.qmltypes
? contrib/qml/QtQml/WorkerScript/qmldir
? contrib/qml/QtQml/libqmlplugin.a
? contrib/qml/QtQml/libqmlplugin.prl
? contrib/qml/QtQml/plugins.qmltypes
? contrib/qml/QtQml/qmldir
? contrib/qml/QtQuick/tooling/Component.qml
? contrib/qml/QtQuick/tooling/Enum.qml
? contrib/qml/QtQuick/tooling/Member.qml
? contrib/qml/QtQuick/tooling/Method.qml
? contrib/qml/QtQuick/tooling/Module.qml
? contrib/qml/QtQuick/tooling/Parameter.qml
? contrib/qml/QtQuick/tooling/Property.qml
? contrib/qml/QtQuick/tooling/Signal.qml
? contrib/qml/QtQuick/tooling/libquicktoolingplugin.a
? contrib/qml/QtQuick/tooling/libquicktoolingplugin.prl
? contrib/qml/QtQuick/tooling/qmldir
? contrib/qml/QtQuick/tooling/quicktooling.qmltypes
? contrib/qml/builtins.qmltypes
? contrib/qml/jsroot.qmltypes

contrib/.gitignore

@@ -12,4 +12,5 @@ plugins
 python-venv
 vlc-contrib-*.tar.xz
 vlc-contrib-*.tar.bz2
+qml
 /*-*-*/