Support tonicExampleFilename in package.json to customize the Tonicdev link in npm

[JogoShugh]

https://tonicdev.uservoice.com/knowledgebase/articles/765846-how-do-i-customize-the-example-for-my-npm-package

You can also put the example in a separate file, if you prefer, and then add this property instead:

"tonicExampleFilename": "example.js"

If you want to read more about the npm/tonic integration, check out this blog post.