Add support for custom utilities

[zweimach]

Add support for custom utilities

Description

This PR adds support for recognizing custom utilities as whitelist classnames for no-custom-classname rule.

Only works on custom utilities and does not support other custom plugins

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

npm test

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

[zweimach]

Please review and refine my small contribution to your preferences, as this is my first time working on ESLint plugins.

[francoismassart]

Thanks I'll take the time to try this out after the weekend.

[thebuilder]

This PR seems to break in a few different ways. All the errors occur in the extractPlugin function:
https://github.com/francoismassart/eslint-plugin-tailwindcss/pull/26/files#diff-b8144a7e4161e7f8b23218be5e95d75a9a3b5a01bf897fd4965c52ec37fb7fa4R40

Using official plugins:

require('@tailwindcss/typography')

TypeError: Error while loading rule 'tailwindcss/no-custom-classname': plugin.handler is not a function

Using addVariant in a custom plugin:

      addVariant('dark', ({ modifySelectors, separator }) => {
        modifySelectors(({ className }) => {
          return `.theme-dark .${e(`dark${separator}${className}`)}`;
        });
      });

TypeError: Error while loading rule 'tailwindcss/no-custom-classname': addVariant is not a function

Using variants:

plugin(({ addUtilities, addVariant, variants, e }) => {
      addUtilities(
        {
          '.flip-x': {
            '--tw-scale-x': '-1',
          },
          '.flip-y': {
            '--tw-scale-y': '-1',
          },
        },
        variants('flip')
      );
    }), 

TypeError: Error while loading rule 'tailwindcss/no-custom-classname': variants is not a function

[thebuilder]

@francoismassart this seems to have broken the plugin in 1.9.0.

[francoismassart]

Yup I'll revert, I had the same issue with theme

[francoismassart]

use v1.9.1 for now, I'll unpublish v1.9.0