Add option listeners

[MisterCheezeCake]

I suggest adding the ability to register listeners for when an option's value is changed.

[lineargraph]

This can already be done with

MoulConfig/legacy/src/main/java/io/github/notenoughupdates/moulconfig/test/TestCategory.java

Lines 62 to 65 in e594eec

	@ConfigOption(name = "Another Text test", desc = "Text Editor Test")
	@ConfigEditorText
	@Expose
	public Property<String> text2 = Property.of("Text 2");

MoulConfig/legacy/src/main/java/io/github/notenoughupdates/moulconfig/test/MoulConfigTest.java

Lines 89 to 91 in e594eec

	testConfig.testCategory.text2.whenChanged((oldValue, newValue) ->
	Minecraft.getMinecraft().thePlayer.addChatMessage(
	new ChatComponentText("Just changed text2 from " + oldValue + " to " + newValue)));

. I intentionally removed / deprecated the runnableId way of specifying update events since it involved a lot of magic constants. If you have another wish for how to listen to update events, or a reason to bring back the annotation with runnableId, lmk.