Include license header in the package.json

LICENSE

@@ -1,4 +1,4 @@
-Copyright (c) 2013 Martin Aspeli
+Copyright (c) 2013-2018 Martin Aspeli, 2018-2020 Andrii Kurdiumov
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

package.json

@@ -15,10 +15,11 @@
       "email": "optilude@gmail.com"
     },
     {
-      "name": "Andrey Kurdyumov",
+      "name": "Andrii Kurdiumov",
       "email": "kant2002@gmail.com"
     }
   ],
+  "license": "MIT",
   "repository": {
     "type": "git",
     "url": "http://github.com/optilude/xlsx-template.git"