LinkReferenceDefinition takes over sourceSpans from a block following it #315

import org.commonmark.node.Node;
import org.commonmark.parser.IncludeSourceSpans;
import org.commonmark.parser.Parser;

public class Main {
    public static void main(String[] args) {
        Parser parser = Parser.builder().includeSourceSpans(IncludeSourceSpans.BLOCKS).build();
        String input = "[foo]: /url\n\"title\" ok";
        Node node = parser.parse(input);
        System.out.println("LinkReferenceDefinition spans: " + node.getFirstChild().getSourceSpans());
        System.out.println("Paragraph(last child)   spans: " + node.getLastChild().getSourceSpans());
    }
}