QSortFilterProxyModel: Add support for Qt::MatchFlag(s)

It would be helpful to add support for this enumeration in the QSortFilterProxyModel API:

https://doc.qt.io/qt-5/qt.html#MatchFlag-enum

Similarly to this matching API: https://doc.qt.io/qt-5/qabstractitemmodel.html#match

Currently, QSortFilterProxyModel has these methods:

https://doc.qt.io/qt-5/qsortfilterproxymodel.html#setFilterFixedString

https://doc.qt.io/qt-5/qsortfilterproxymodel.html#setFilterRegularExpression

https://doc.qt.io/qt-5/qsortfilterproxymodel.html#setFilterWildcard

But it would be good to have the convenience of exact match, starts with, ends with, etc, even though it is possible to achieve this with regular expressions, I think. Would be helpful not to have to think of regular expression syntax for these common ones.