Add possibility to configure this plugin through a config file

[LvffY]

Hi

This plugin seems to be able to solve an very old pylint issue, so first : thanks for that :)

But because we can have a very large number of promoted/demoted issues, it would be very useful to be able to configure this plugin through a configuration file.

Multiple ideas here :

• Use for pylint configure files (like pylintrc)
• Use an external file (e.g. a YAML file) that would contain our configurations (and mostly our long list of promoted/demoted rules)

I don't think there is a preference for any of the two options here :)

[teake]

Hi, configuration via pylintc or pyproject.toml is already possible. I've added a section to READM.md that describes how in 3582b6c.

Since you're talking a large number of issues that need to be configured, perhaps it's wiser to use pyproject.toml, since in TOML you can split out arrays over multiple lines.

I'm assuming this covers your needs, so I'm closing this issue. If not, feel free to reopen.