This patch extends the documentviewer demo to use
text based translation for English and German, as follows:
- Add AbstractView::addTranslation(fileName) for inheriting
plugin classes to optionally load own translations.
- Implement runtime translation switching. Provide option for
plugins to benefit, if they implement their own runtime
switching functionality.
Task-number: QTBUG-71856
Change-Id: Ic7782b7fa38d1121b140351f5eaa88ac027a6bcd
Reviewed-by: Kai Köhne <kai.koehne@qt.io>