Updating related field does not trigger update.

[1cgonza]

Not so much of an issue but a question or feature request:

If I have a M2O or M2M field and update the values in those collections, the changes are not reflected on the collection I am indexing.

Following your example, a simplified config with "products" as the indexed collection with a M2O field called "category":

"collections": {
	"products": {
		"fields": ["title", "category.title"]
	}
}

If I go to the collection holding the categories and change the "title", those changes do not trigger an update on all the indexes that relate to it.

Is it possible to keep them on sync?

BTW, thanks for the extension, great job!