frame: false doesn't remove the titlebar's background color

[iuriineves]

Description

Setting frame: false on the MicaBrowserWindow options doesn't not get rid of the background color the title bar has.

Changing the titlebar's color using win.setCaptionColor() does change the color of the little "strip", which indicates it is indeed the titlebar.

This issue is very similar to (if not the same as) issue #13. Changing the system setting "Show accent color on title bars and windows borders" seems to fix the issue, might look into that.

Screenshots

Expected

Actual Result

To Reproduce

Create a MicaBrowserWindows with the setting frame: false while having the system setting "Show accent color on title bars and windows borders" turned on.