Feature: Custom accent color

### What feature or improvement do you think would benefit Files?

For now, the only way to customize the color of UI icons is to change the accent color directly from Windows settings.
So my suggestion is to add a setting to change the accent color only for Files, or at least an option to customize UI icons color.

### Requirements

- Adding an option in Appearance settings to select the accent color would be ideal.
- Failing that, an option in the same menu to change specifically UI icons color work as well.

### Files Version

3.9.1.0

### Windows Version

10.0.26100.3775