feat: Add sprintf variable (#3185)

[TheStaticMage]

Description of the Change

This adds a replacevariable $sprintf[template, ...args] that wraps https://www.npmjs.com/package/sprintf-js.

Applicable Issues

Fixes https://github.com/crowbartools/Firebot/issues/3185

Testing

I created a preset effect list that executes chat feed alerts for the three examples in the variable definition.

Screenshot confirms correct output.

Screenshots