chore: publish necessary files only (#2433)

.editorconfig

@@ -11,3 +11,6 @@ insert_final_newline = true
 
 [*.yml]
 indent_size = 2
+
+[*.json]
+indent_size = 2

package.json

@@ -3,6 +3,12 @@
   "version": "0.6.6",
   "description": "D3-based reusable chart library",
   "main": "c3.js",
+  "files": [
+    "c3.js",
+    "c3.min.js",
+    "c3.css",
+    "c3.min.css"
+  ],
   "scripts": {
     "start": "static -p 8080 htdocs/",
     "lint": "jshint --reporter=node_modules/jshint-stylish src/ spec/",