gtkmm comes without schemas

[PointClouder]

Is your feature request related to a problem? Please describe.
When I want to build a gtkmm3 application with and open-file-dialog it fails because of missing schemas files. If there is support, I failed to find a documentation

Proposed solution
povide a sample schema to use with an application and ideally give it a credible win10 look.

Describe alternatives you've considered
Followed this advice:
https://www.gtk.org/download/windows.php
Hardly managed to get it working.

[Illation]

I also had this issue and solved it by getting the schema files from this repo as a submodule: https://github.com/tschoonj/GTK-for-Windows-Runtime-Environment-Installer