Multiple effects on a stage

[NebelFox]

Is your feature request related to a problem? Please describe.

A stage is limited to only one effect

Describe the solution you'd like

Idea:
Ability to apply multiple effects on reaching a stage, with duration and amplifier specified individually for each effect.

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Examples of usage:

• on fatigue between 0 and 20 player gets permanent speed, but also gets hunger for 10 seconds.
• on fatigue between 90 and 100 player gets blindness for 10 seconds, and permanent slowdown III

Additional context

Suggestions for stage format in config:

• min, max, potion_id, duration, amplifier, [potion_id, duration, amplifier], ...
• min, max, potion_id:duration[:amplifier], potion_id:duration[:amplifier], ...

Here [] mean optionality, not a list!