New Gamemode: Opposite Days

[impostor4291]

Describe the feature
In Opposite Days, the Crewmates and Impostors swapped their objectives.
Impostors have to eliminate all Crewmates,or gain enough scores by sabotaging to win.(the sabotage will be automatically fixed in 10s)
Crewmates need to outnumber the Impostors to win.
[Additional info about this gamemode]
When a Crewmates finishes all of their tasks,they will get the Kill button,and Impostors' scores will be decreased.
Depending on settings,special roles may spawn mid-game.

Why is this needed?
Players may get bored with the Standard mode and want to try new gamemodes.
However,TOHE has only 3 gamemodes(Standard,FFA,Speedrun) for players to choose.

[github-actions]

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