Style Titlebar When Window is Inactive

Change the style of the titlebar to be the inactive variant (for all XP, 98, and 3.1) when the window is detected to inactive.

This ability is added in Wails v3 with the `Window` `WebviewWindow.IsFocused` method. See PR: https://github.com/wailsapp/wails/pull/ 3295

This project first needs to be updated to Wails v3 when it is released.