Look for spellchecker libraries in QStandardPaths::AppDataLocation

On Windows and Linux, Qt WebEngine tries to locate spellchecker dictinoaries in a few locations:

• QTWEBENGINE_DICTIONARIES_PATH
• QCoreApplication::applicationDirPath()/qtwebengine_dictionaries
• [QLibraryInfo::DataPath]/qtwebengine_dictionaries

(see also https://doc.qt.io/qt-5/qtwebengine-features.html#spellchecker) .

Note that all the hardcoded paths will typically be only writable by an administrator. Qt WebEngine should therefore arguably use QStandardPaths::locate(QStandardPaths::AppDataLocation, "qtwebengine_dictionaries", QStandardPaths::LocateDirectory). This can also replace QCoreApplication::applicationDirPath()/qtwebengine_dictionaries .