Sync cursor blink rate

Particularly the ability to turn the blinking off is important.

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in ~/.config/kdeglobals put

[KDE]
CursorBlinkRate=0

• No more blinking cursor in Gimp (GTK 2)
• No more blinking cursor in Flatpak gedit (GTK 3)
• No more blinking cursor in Flatpak TextEditor (GTK 4)
• No more blinking cursor in Firefox