Add (to QUrl help) references to `matches()`

Dear Qt developers:

In the help pages:

• In [bool QUrl::operator==(const QUrl &url) const](https://doc.qt.io/qt-5/qurl.html#operator-eq-eq):
  A "See also `matches()`." would be helpful and would avoid confusions.

• In [bool QUrl::operator!=(const QUrl &url) const](https://doc.qt.io/qt-5/qurl.html#operator-not-eq):
   A "See also `matches()`." would be helpful and would avoid confusions.

And thanks for making Qt better.