Add EditFlags and MediaFlags to Quick and Widget API

- EditFlags shows the available edit actions
- MediaFlags shows the status and available actions of the current media element
- Update the documentations
- Register ContextMenuRequest 1.1
- Update plugins.qmltypes

[ChangeLog][QtWebEngine][QtWebEngineWidgets] Add EditFlags and MediaFlags to the APIs

Change-Id: Ia7603696a291df5465c5e612adc2456f5f6cb479
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Peter Varga <pvarga@inf.u-szeged.hu>
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>