Internet Explorer/Edge has Smooth Scrolling, Firefox has Smooth Scrolling, Chrome is testing a experimental Smooth Scrolling. Opera has Smooth Scrolling, working and pretty smooth too, but it can't be enabled by any means, except by adding "--enable-smooth-scrolling" at the end, as a parameter in a Windows shortcut.
My suggestion: add an option to enable the native Smooth Scrolling that Opera already have. While the Smooth Scrolling may be an experimental thing right now, place that option in the proper place for experimental thing under the advanced Settings options, in the Power User settings options, or under the opera://flags options.
Smooth Scrolling is a very valuable feature of any browser. You scroll on practically every page, and the most smooth and fluid the scroll is, the faster and more responsive the browser feels.