Request to add DataGrid style

[rakuten]

I just want to tell you that material.avalonia project is really great.

But I found that the style of DataGrid has not been defined yet.

https://github.com/AvaloniaUI/Avalonia/blob/master/src/Avalonia.Controls.DataGrid/Themes/Default.xaml

[appleneko2001]

DataGrid style are still WIP (working in progress). It looks like this now:

DataGrid with other controls (buttons, checkbox etc.) is still not tested. So I don't know how it looks like, but we will know later.

[SKProCH]

Seems like this is working.