Specify NodeJS 12 as a requirement.

When I installed this for local use, I got several warnings and errors.  Upgrading to NodeJS latest (version 12) fixed all the issues.

Author: StevenBlack

readme.md

@@ -39,6 +39,8 @@ curl https://corona-stats.online?format=json
 
 ## Local Command (For coloured ouput)
 
+We recommend NodeJS version 12 which you can download [here](https://nodejs.org/en/download/).
+
 **Install**
 
 ````sh