Update plugin registration documentation about entry points

[Victorien]

describe the request

Hello,

The documentation currently states:

Flake8 relies on functionality provided by setuptools called Entry Points. These allow any package to register a plugin with Flake8 via that package’s setup.py file.

Any interest in having this part of the documentation updated to point to the Packaging user guide instead, so that people can be aware this is not a setuptools-only feature anymore?

(Without changing the setup.py example, I believe it is still up to date?)

[Ian Stapleton Cordasco]

Sure. If merge a PR that updates that. For reference pkg_resources is also deprecated for a library in the standard library so it's worth mentioning that too

[pomponchik]

It could be great add something about setting up by pyproject.toml file.

[Ian Stapleton Cordasco]

The packaging user guide already has examples for all types of package metadata config so that doesn't need to be replicated here

[Victorien]

Yes I was thinking more about linking the packaging user guide, and explicitly stating "we give an example with setuptools (and setup.py) but this is now a standard blabla.."

Will probably have time to work on this by the end of the week