ModLoader.AddMod should check for an already present mod

[Banane9]

Log a warning when already present, only log addition and fire event when not.

MonkeyLoader/MonkeyLoader/MonkeyLoader.cs

Lines 276 to 284 in 0edf5df

	public void AddMod(Mod mod)
	{
	Logger.Debug(() => $"Adding {(mod.IsGamePack ? "game pack" : "regular")} mod: {mod.Title}");
	_allMods.Add(mod);
	NuGet.Add(mod);
	ModAdded?.TryInvokeAll(this, mod);
	}

if(_allMods.Add(mod))
    // Add
else
    // Warn

Spawned by:
ResoniteModdingGroup/MonkeyLoader.GamePacks.ResoniteModLoader#18