Update nucleotide-count topics as in #808

Added @FridaTveit suggestions to nucleotide-count topics

config.json

       "topics": [
         "conditionals",
         "exception_handling",
+        "integers",
+        "maps",
         "parsing",
-        "searching"
+        "searching",
+        "strings"
       ],
       "unlocked_by": "hamming",
       "uuid": "2d80fdfc-5bd7-4b67-9fbe-8ab820d89051"