automatically determine number of custom questions

export.py

@@ -65,7 +65,7 @@ def process(reader: csv.reader) -> Dict[str, List[Signup]]:
             1 for fieldname in reader.fieldnames if fieldname.startswith('Question ')
     )
 
-    for linenum, line in enumerate(reader):
+    for line in reader:
         date, slot = line['Start Date & Time'].split(' ')
         assert date == DATE, date