Replace gulp-sass-lint with gulp-postcss / stylelint

[agibson-godaddy]

Issue: https://godaddy-corp.atlassian.net/browse/MWC-17960

Summary

This replaces the unmaintained gulp-sass-lint with gulp-postcss / stylelint. It also adds a lint config, which disables a ton of rules just to avoid suddenly switching to this method and ending up with a ton of warnings you didn't have before. IMO it's up to individual plugins to override these lint rules (supported).

To override:

Create a new .stylelintrc.json file in plugin directory with desired rules.

Update sake config:

  // sake.config.js
  module.exports = {
    tasks: {
        lint: {
            stylelintConfigFile: '.stylelintrc.json'
        }
    }
    // ... other sake configuration
  }

QA

1. Use a plugin that has SCSS - https://github.com/gdcorp-partners/woocommerce-customer-order-csv-export/pull/107
2. Use this development version of Sake
3. In the plugin's directory, run sake lint:scss
   • No errors
4. Run sake compile:scss
   • No errors
   • CSS renders okay

[Copilot]

Pull request overview

This PR replaces the unmaintained gulp-sass-lint package with a modern stylelint-based linting solution using gulp-postcss and stylelint. The change includes a default configuration that disables many rules to maintain compatibility with existing projects while allowing individual plugins to override settings via their own .stylelintrc.json files.

Changes:

• Removed dependency on deprecated gulp-sass-lint and added stylelint, postcss-scss, and related packages
• Updated the SCSS linting task to use postcss pipeline with stylelint
• Added a default stylelint configuration with many rules disabled for backward compatibility

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 1 comment.

File	Description
tasks/lint.js	Updated lintScssTask to use postcss/stylelint instead of gulp-sass-lint, with support for custom config files
package.json	Removed gulp-sass-lint dependency and added stylelint, postcss-scss, and stylelint-config-standard-scss
lib/lintfiles/.stylelintrc.json	Added default stylelint configuration extending standard SCSS config with many rules disabled

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