Fix Contributing Guide across kedro, kedro-plugins

[noklam]

Description

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Re-assess CONTRIBUTING.md in both kedro, kedro-plugins and the documentation to make sure this is easy enough for developers to setup a local development environment

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[stichbury]

I think we definitely need to make a few updates to https://docs.kedro.org/en/latest/contribution/index.html to align the content in the page with the table of contents and also make this documentation page consistent with the separate markdown in CONTRIBUTING.md

[astrojuanlu]

I'm on the fence about that, maybe we should remove that page completely as we said in #2376

But definitely we could have a section, say, on GitHub Wiki, and make the CONTRIBUTING.md files pretty minimal, with a link there that we can update without going through the toil of CI.

[merelcht]

We need to clarify what types of contributions we accept, specifically for kedro-plugins mention that dataset additions are the most likely to get accepted. But of course don't discourage anyone from helping out on kedro-airflow etc.

[stichbury]

I won't tackle this but it's a good ticket if anyone wants to learn more about our contribution process and pick up some docs writing experience.

[astrojuanlu]

One thing that came up after talking with @laizaparizotto: our make test plugin=x for kedro-plugins is not documented anywhere right? Or am I missing something?