Add support for QRegularExpression in QML

Currently QRegularExpression is not supported in QML
QRegExp is supported, you can have a QRegExp property that's settable from QML:

myRegExpProp: /\w+foo/i

It would be nice to have that for QRegularExpression since QRegExp should be avoided.

The workaround is to have a pattern property and a couple of other properties for the options, or a flag property if you want to support all options (that means having to expose the flag values by copying the enum and using Q_FLAG).