ContextMenu represents a context menu containing
ContextMenuItem<!-- -->s in a WebKitWebView.
When a WebKitWebView is about to display the context menu, it emits the WebKitWebView::context-menu signal,
which has the ContextMenu as an argument. You can modify it, adding new submenus that you can create with
ContextMenu, adding new
ContextMenuItem<!-- -->s with
prepend, append
or insert, maybe after having removed the existing ones with
remove_all.