📦 Release web-features@3.9.1

[github-actions]

This is a generated release pull request. Don't merge if you're not ready to carry out the release.

## What's Changed
* Bump @mdn/browser-compat-data from 7.1.20 to 7.1.21 by @dependabot[bot] in https://github.com/web-platform-dx/web-features/pull/3536
* Add stylelint-plugin-use-baseline to Baseline in the wild by @ryo-manba in https://github.com/web-platform-dx/web-features/pull/3233

## New Contributors
* @ryo-manba made their first contribution in https://github.com/web-platform-dx/web-features/pull/3233

**Full Changelog**: https://github.com/web-platform-dx/web-features/compare/v3.9.0...v3.9.1

Subscribe to the [Upcoming changes](https://github.com/web-platform-dx/web-features/discussions/2613) announcements thread for news about upcoming releases, such as breaking changes or major features.

[ddbeck]

v3.9.0

{
  "features": 1099,
  "compatKeys": 14120,
  "compatKeysUnmapped": 2923,
  "compatCoverage": 0.8284926362729567,
  "compatKeysPerFeatureMean": 12.848043676069153,
  "compatKeysPerFeatureMedian": 4,
  "compatKeysPerFeatureMode": 1,
  "currentBurndownSize": 1988
}

main

{
  "features": 1099,
  "compatKeys": 14120,
  "compatKeysUnmapped": 2926,
  "compatCoverage": 0.8283468262348939,
  "compatKeysPerFeatureMean": 12.848043676069153,
  "compatKeysPerFeatureMedian": 4,
  "compatKeysPerFeatureMode": 1,
  "currentBurndownSize": 1990
}