Add option to import/export bookmarks or include it in OPML

[KraXen72]

Pleae add the option to import/export bookmarks or include it in OPML currently if i check the opml export there's no mention of my bookmarks. i'd rather them not be lost when they get sufficiently old or when i switch devices/reinstall.

Thanks for the great feed reader!

[prof18]

Good point, thx for the suggestion!