Contributing guidelines still mention Poetry instead of PDM

[BartSchuurmans]

First Check

• I added a very descriptive title here.
• I used the GitHub search to find a similar question and didn't find it.
• I searched the SQLModel documentation, with the integrated search.
• I already searched in Google "How to X in SQLModel" and didn't find any information.
• I already read and followed all the tutorial in the docs and didn't find an answer.
• I already checked if it is not related to SQLModel but to Pydantic.
• I already checked if it is not related to SQLModel but to SQLAlchemy.

Commit to Help

• I commit to help with one of those options 👆

Example Code

n/a

Description

The contributing guidelines mention Poetry for development of SQLModel, but I see the project has migrated to PDM

Operating System

Linux

Operating System Details

No response

SQLModel Version

n/a

Python Version

n/a

Additional Context

No response