Create aliases for .html documentation pages without the suffix

Sometimes it is probably faster to jump to some other documentation on docs.qt.io by just changing the name in the address bar. However, the page names end with .html so it means either that has to be written too or the address edited in the middle of the text.

For example if this:

https://doc.qt.io/qt-5/qwidget.html

could also be accessed with:

https://doc.qt.io/qt-5/qwidget