Move snapshotting behaviour into the types

[thegedge]

Based on this comment, we could move a lot of the MQT snapshotting behaviour into the types themselves. That way we could avoid hardcoding a ton of logic in a single function, like how we deal with snapshotting references in an array/map:

mobx-quick-tree/src/snapshot.ts

Lines 26 to 32 in 918bddd

	const type = getType(value) as MapType<IAnyType>;
	const childrenAreReferences = isReferenceType(type.childrenType);
	return Object.fromEntries(
	Array.from(value.entries()).map(([k, v]) => {
	return [k, childrenAreReferences ? v[$identifier] : snapshot(v)];
	})