added "Yarn" as requirement

setup_root.md

@@ -10,6 +10,7 @@ Zendro consists of four source-code projects: __graphql-server-model-codegen__,
 
 ## Project Requirements:
  * [NodeJS](https://nodejs.org/en/) version 14+ is required.
+ * [Yarn](https://classic.yarnpkg.com/lang/en/docs/install/#debian-stable) 
 
  **recommended for setting up zendro using docker**
  * [docker](https://docs.docker.com/get-docker/)