fix: publish TypeScript typings in "files" attribute and reference th…

…em in package.json "typings" attribute (#60)

* Create index.d.ts

typings for TS

* Update index.d.ts

* Update package.json

package.json

@@ -18,9 +18,11 @@
   "license": "MIT",
   "author": "Keith Cirkel <npm@keithcirkel.co.uk> (http://keithcirkel.co.uk/)",
   "files": [
-    "index.js"
+    "index.js",
+    "index.d.ts"
   ],
   "main": "index.js",
+  "types": "index.d.ts",
   "bin": "index.js",
   "scripts": {
     "semantic-release": "semantic-release",