Add some contributing guidelines

Author: Andreas Savvides

README.md

@@ -28,6 +28,13 @@ python server.py
 
 Head over to `localhost:5000` and you should be able to see this code in action; try and log in using Digits!
 
+## Contributing
+
+All contributions are welcome; fork the repository, make your changes and open a pull request. Try to stick to the coding conventions that are already in place.
+
+At the moment, what would be most useful is adding code to show an end-to-end solution of how to use Digits. At present we only show how this is done using a Python back-end.
+Have a look at the [issue tracker](https://github.com/AnSavvides/react-digits/issues) and feel free to say you are interested to work on something that has not already been assigned. Right now we have open tickets for building [Ruby](https://github.com/AnSavvides/react-digits/issues/1), [node.js](https://github.com/AnSavvides/react-digits/issues/3), [Lua](https://github.com/AnSavvides/react-digits/issues/2) and [Go](https://github.com/AnSavvides/react-digits/issues/4) back-ends. If you want to add support for another language, feel free to open an issue!
+
 ## Notes
 
 - Digits is not available as an npm package, but rather over CDN; because of that, we had to include the Digits web SDK over CDN & reference it in our `webpack` configuration in [`externals`](http://webpack.github.io/docs/library-and-externals.html). As a side effect, this is stopping us from creating this solution as a reusable npm-installable component.