Expand the multiplier feature on nukes and buildings for high gold games

## Purpose

After [this game](https://openfront.io/w5/game/debuuZU1), the limitations of clicking fast with a 5x nuke multiplier became very clear (Input gets locked) so I propose that hitting the hotkey should increase the amount by 5 every time, to make having a ton of silos actually useful and break these horrible stalemates.

## Assignment

- [X] I'd like to be assigned to this issue and work on it myself
I have the code already, it's 3 lines + tests.
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[Discord:Pesinario]