readme : update tools list (#9475)
* Added link to proprietary wrapper for Unity3d into README.md
Wrapper has prebuild library and was tested on iOS, Android, WebGL, PC, Mac platforms, has online demos like [this](https://d23myu0xfn2ttc.cloudfront.net/rich/index.html) and [that](https://d23myu0xfn2ttc.cloudfront.net/).
* Update README.md
Fixes upon review
