Propose an implementation for PsySH

[shavounet]

Description

https://psysh.org/

Should be inside an external composer package.
The goal is to provide breakpoints between task executions, allowing to inspect intput / output.
Proposed features :

• break between every task
• on each break point step by step / continue util the end / stop / skip
• provide a syntax to use conditional breakpoints ("break after my_task after 3000 iteration", or "break after my_task if output === X")

Requirements

• Documentation updates
  • Reference
  • Cookbooks
  • Changelog
• Unit tests

Breaking changes

None