Scripting API: version() does not indicate windowing system / display server

Several CopyQ bugs/issues on GNU + Linux/BSD depend on the windowing system/platform. Unfortunately, it can take time to get information on the display server used, because while the bug reporting template suggests `copy(version())`, [`version()`](https://github.com/hluk/CopyQ/blob/master/src/scriptable/scriptable.cpp#L717) does not indicate the platform.

For example, the initial body of ticket #3416 did not include that information.

**Describe the solution you'd like**
It would be good if, when running on GNU OSs, a line indicating the windowing system like KInfoCenter’s “Graphics Platform” would be added to `version()`. Ideally, this would be fed by [QSysInfo](https://doc.qt.io/qt-6/qsysinfo.html), but this would apparently need an upstream change as I don't see any member providing that.

**Describe alternatives you've considered**
To avoid blocking on Qt, we could steal [KInfoCenter’s code/algorithm](https://github.com/KDE/kinfocenter/blob/master/kcms/about-distro/src/GraphicsPlatformEntry.cpp), which is freely licensed C++. It is fairly simple, although a little hacky/fragile. Perhaps [QWaylandCompositor](https://doc.qt.io/qt-6/qwaylandcompositor.html#details) could be used to replace the Wayland case.

Even better than just the system/platform would be to indicate the display server (for example X.org, KWin or Mutter).

**Additional context**
Obviously, such information does not belong in a “version string”, but I guess it is time to acknowledge that `version()` no longer returns just the version. The specification could be adapted, and perhaps the function can even be renamed something like `getDiagnosticInfo()`.

License
This report (including all messages and attachments I add to it) is offered under the terms of CC0 1.0.