Add new translator for Bundesgesetzblatt (Federal Law Gazette of Germany...

...)

 * It should be freely available online. Can you access it outside from Germany (see test cases)?
 * I would like to attach the pdf directly to the entry, but it didn't suceed so far (iframe, embedded pdf, ...)
 * The icon seems sometimes not to update. It might just be a dom change and not a real new page load. What was the trick here again?
 * AFAIK the end page is not available.
 * Any other comments?
I wouldn't. In law, citing just the first page is common. Zotero would handle this on CSL export either way, but people looking through their data might get confused or feel compelled to delete the en dash.