Improve docs with details about the use of GPL components from Chromium

There are a few 3rd-party components in Chromium which are licensed under GPL. They are used to build software artefacts, rather used for other purposes. 

The table of licenses and the text on https://doc.qt.io/qt-6/qtwebengine-licensing.html does not explain this. And the text before the list says "Third party licenses included in the sources are”. Reading this, a user can make confusing assumptions. 

This doc should be extended to explain the use of component which are under GPL