Modifier Keys and full keymap from Dear ImGui

[classner]

Hi @nmwsharp !

Thanks for this amazing package! I'm currently designing a tool that is using Polyscope and makes heavy use of keyboard controls. For that, it would be invaluable to have access to modifier keys as well as the full set of keys from the keyboard. However, currently in the Polyscope Python interface only a few keys are mapped (see https://github.com/nmwsharp/polyscope-py/blob/11362b1bf663e66bf8876af6909629ebd3c79791/src/cpp/imgui.cpp#L1704 and following) and the modifier keys, even though exposed in the map, can not be checked (GetMergedModFlags from ImGui is not exposed, neither is the io module to read io.KeyMods, if I'm not mistaken).

Is there currently a way to read modifier keys in Polyscope in Python that I'm missing? Would it be possible to expose access to the io module or another access function? Could we extend the list of mapped keys to cover the entire keyboard instead of the current selection?

Thanks a lot in advance! Christoph