Add onChange handler

[HLXII]

There might be some cases where you want to trigger some code when a setting is changed. A couple of examples:

• You're using a separate handling of dark theming from TailwindCSS that modifies the data-theme of the page.
• Changing a setting requires additional handling that's not fully handled by Vue.
• Possibly in the future when KeyBinding settings are implemented, you will want to update the Keybind whenever the player changes that setting.

Working off of the event handling for Achievements, I've added an onChange event dispatcher to the base Setting class. I couldn't match the Achievements implementation exactly since it's possible to update the setting value from the Setting instance directly, rather than it being fully controlled by the base Feature. It's also probably better to have individual subscriptions since you only want change handlers for specific settings anyways.

Also for this implementation I had to fix BooleanSetting to use the set method so it'll dispatch the onChange event as well.

[Ishadijcks]

Great addition, I think it can be merged!

Do you think the old value should be passed along the event as well?

[HLXII]

I can't think of any scenarios where you'd want to know the previous value, but it's probably safer to just implement it now in case it's necessary in the future.

[Ishadijcks]

I suggest using the regular EventDispatcher which takes 2 arguments instead of an array with a fixed length

[HLXII]

The EventDispatcher uses a sender and arguments no? I'm not entirely sure what you mean since it would just be EventDispatcher<Setting, number[]>.

[Ishadijcks]

No the first argument doesn't have to be the sender

protected _onChange = new SimpleEventDispatcher<SettingsValue, SettingsValue>();

And invoke with

_onChange.dispatch(prevValue, newValue)

Instead of having an array with length 2