chore: updated README about OS limits during local development

Author: oboukili

README.md

@@ -328,6 +328,10 @@ docker pull ghcr.io/dexidp/dex:v2.27.0
 docker pull redis:5.0.10-alpine
 ```
 
+#### Troubleshooting during local development
+
+* **"too many open files":** Running all acceptance tests in parallel (the default) may open a lot of files and sockets, therefore ensure your local workstation [open files/sockets limits are tuned accordingly](https://k6.io/docs/misc/fine-tuning-os).
+
 ---
 
 ## Credits