Replaced text smiley with img smiley in the README

Author: castarco

README.md

@@ -23,7 +23,7 @@ ColorSharp is available as a [nuget package](https://www.nuget.org/packages/Colo
 
 ## How to contribute
 
- * First of all, you can take a look on the [TODO list](https://github.com/Litipk/ColorSharp/blob/master/TODO.md) and decide if there is something that you want to do :) . If you think there are missing improvements in this file, then you are invited to modify the TODO list.
+ * First of all, you can take a look on the [TODO list](https://github.com/Litipk/ColorSharp/blob/master/TODO.md) and decide if there is something that you want to do :wink: . If you think there are missing improvements in this file, then you are invited to modify the TODO list.
  * You can also send us bug reports through the [tracker](https://github.com/Litipk/ColorSharp/issues), or look for bugs to solve.
  * If you are really interested on helping to improve ColorSharp, we recommend to read the [contributing guidelines](https://github.com/Litipk/ColorSharp/blob/master/CONTRIBUTING.md).