Add support for window-tool-bar, added in Emacs 30.

[chaosemer]

I am the author of the "window-tool-bar" package which was recently added to Emacs 30. I'm now chasing down popular themes so that it looks good when Emacs 30 is released.

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• [x] The commits are consistent with our contribution guidelines
• [x] You've added a before/after screenshot illustrating visually your changes.
  • Before:
  • After:
• [x] You've updated the changelog (if adding/changing user-visible functionality - e.g. theme new faces/packages, changing existing faces, etc)
• [x] You've updated the readme (if adding/changing configuration options)
  • Note: No configuration added

[bbatsov]

@chaosemer I think the "before" and "after" screenshots are the same. :-)

[impaktor]

@bbatsov If you look at the two pressed(?) buttons, the house icon and the one next to it, they look different.

[bbatsov]

Ah, got it.