Add word "summe" in rules for correct compound word pronunciation

I hope that will be my last change. Most of them, like Zitat, gedulds, etc have been added for correct compound word pronunciation. The A: phoneme in komma and beta sounds more natural for me; I also did Komma this way because it matches the way espeak reads it when written as an actual word.

dictsource/de_rules

@@ -1103,6 +1103,7 @@ screen	_^_EN
      _) sky        _^_EN
         soldat     z%OldA:t
      &) so (rt_    s_|O
+        summe	zUm@
 
         speed      _^_EN
   stau) ss         s