Add playground mention in blog post

Author: ryyppy

_blogposts/2021-02-09-release-9-0.mdx

@@ -21,6 +21,8 @@ Use `npm` to install the newest [9.0.0 release](https://www.npmjs.com/package/bs
 npm install [email protected] --save-dev
 ```
 
+You can also try our new release in the [Online Playground](/try).
+
 In this post we will highlight the most notable changes. The full changelog for this release can be found [here](https://github.com/rescript-lang/rescript-compiler/blob/master/Changes.md#90). 
 
 ## Compiler Improvements