Create Windows build in CI

[wjt]

Add the Windows build to our CI builds. Like the Linux/Flatpak build, to save electrons this should run in these cases:

• Making a release
• Manually running a build and checking a "build for Windows" box
• When the files which affect the Windows build specifically (GitHub Actions workflow, export_presets.cfg, any Windows-specific files) change

Otherwise it should not be built automatically.

XP Summary (total 450)

Subdomain	Skill	XP
Engineering: Optimization & Performance	Problem Solving	150
Engineering: Optimization & Performance	Creativity & Design Thinking	150
Engineering: Optimization & Performance	Technical Literacy	150