[Feature]: Add extender placeholders to be used in combatNotification

[CitralFlo]

Is your feature request related to a problem?

I want to use actionBar to display "Seconds left in combat: {TIME}" for my players but with current configuration the output is: "Seconds left in combat: 30s" meaning that seconds are doubled.

Describe the solution you'd like

Placeholder that supports:
using spaces, comas, value with metric or just value

Describe alternatives you've considered

#355

Additional context

Reported by user on discord