Suggestion: Add Double Doors functionality

[Romz24]

It would be nice to have a built-in tweak that automatically opens and closes both doors in a double-door setup when interacting with either door.

This is a small but very useful QoL feature that many players use through the Double Doors mod, and it would fit perfectly within UniversalTweaks' collection of vanilla-friendly tweaks.

Reference implementation:
https://www.curseforge.com/minecraft/mc-mods/double-doors