Gtk.TextIter.prototype.forward_sentence_end

function forward_sentence_end():Boolean {
    // Gjs wrapper for gtk_text_iter_forward_sentence_end()
}

Moves forward to the next sentence end. (If iter is at the end of a sentence, moves to the next end of sentence.) Sentence boundaries are determined by Pango and should be correct for nearly any language (if not, the correct fix would be to the Pango text boundary algorithms).