Search methods added to the WebView control

[Benoît Minisini <benoit.minisini@xxxxxxxxxxxxxxxx>]

Hi,

In the last commit, I added three methods for searching text in the 
contents of a WebView (in GTK+3, QT5 and QT6 webview components).
'Find(<string>, <options>)' starts a new search and highlights all the 
found strings. It returns the number of matches.
The only option supported in common by Qt and WebKitGTK+ is case 
sensitivity. WebKitGTK+ have others, but not Qt. What a pity!
'FindNext()' and 'FindPrevious()' will then search forward or backward.

If you want to end the search and hide the highlighting, just call 
'Find()' with no arguments.
Enjoy!

--
Benoît Minisini.