added basic typescript definition file (euvl#121)

* added basic typescript definition file * adde new line on definition file

Author: adrianthedev

index.d.ts

@@ -0,0 +1 @@
+declare module 'vue-js-toggle-button'

package.json

@@ -10,6 +10,7 @@
  "build": "npm run build:client && npm run build:ssr"
  },
  "main": "dist/index.js",
+ "types": "index.d.ts",
  "repository": {
  "type": "git",
  "url": "https://github.com/euvl/vue-js-toggle-button.git"