Animate red flash for blocking pause dialogs

[SaberShip]

Very small QOL improvement to flash a red pulse (like the threat letters) under the blocking pause indicator.

Given a non-async time game is running
When a player opens a dialog that pauses the game
Then a red pulse will be animated periodically near the colonist bar's blocking pause indicator for all players.

Multiple simultaneous blocking pauses from different maps will flash independently.
I chose 6 seconds as the pulse interval.