[stylelint] improvements to stylelint rule (docusaurus/copyright-header)

[yangshun]

💥 Proposal

This is a follow up of #2361 and #2363 regarding improving our stylelint test (packages/stylelint-copyright)

• It is using the Tape test runner and is not integrated into our CI. If we move the implementation to Jest, it'll be run as part of the repo root's yarn test flow which is part of CI and that'll be great. stylelint's rules are already using Jest and perhaps we can learn from how they do it
• Allow for rule configuration options to specify the copyright pattern similar to eslint-plugin-header

Have you read the Contributing Guidelines on issues?

Yes

[ayshiff]

I would love to work on it @yangshun 👍

[yangshun]

@ayshiff go ahead

[ayshiff]

Hey @yangshun, I have a question about the way stylelint rules should be tested !

I followed the way stylelint's rules were tested by adding a jest setup file and defining a testRule method.
I think I have to do some tricks around the way the plugin is created because it gives me the error "Unknown rule docusaurus/copyright-header."

Otherwise I checked the way "stylelint-test-rule-tape" was working and it uses the version « 9.1.1 » of stylelint where we can access a createRuleTester method to make our own rule tester. We can then create our own assertEquality function using Jest.

I think the best way is to follow the first method but I wanted to have your opinion before.

[yangshun]

Please try to reuse the Jest file at the root of the repo.