Update README.md (#1746)

Author: martin-henz

README.md

@@ -22,7 +22,7 @@ Open-source implementations of the programming language _Source_. Source is a se
 
 - NodeJS v20
 - Python: On MacBook Pro with chip Apple M1 Pro, use python 3.10.12. Here is [the correct way to set Python 3 as default on a Mac](https://opensource.com/article/19/5/python-3-default-mac).
-
+- yarn: use the version specified in `package.json`. On macos, you may need to run `corepack enable`.
 ## Usage
 
 To build,