Fix typo: value for "Insulator" is craft=insulation (#695)

Author: kjonosm

data/fields/craft.json

@@ -30,7 +30,7 @@
             "grinding_mill": "Grinding Mill",
             "handicraft": "Handicraft",
             "hvac": "HVAC",
-            "insulator": "Insulator",
+            "insulation": "Insulator",
             "jeweller": "Jeweller",
             "joiner": "Joiner",
             "key_cutter": "Key Cutter",