Feature request: Use top-level node text as title of OPML export

[tmalsburg]

Example:

* My science RSS feeds                                                   :elfeed:
** [[https://www.annualreviews.org/action/showFeed?ui=45mu4&mi=3fndc3&ai=6690&jc=linguistics&type=etoc&feed=atom][Annual Rev Ling]]

It would be nice if the OPML would use "My science RSS feeds" as the title instead of "Elfeed-Org Export".