Bump stylelint from 15.7.0 to 15.8.0 in /src/Costellobot (#671)

Bumps [stylelint](https://github.com/stylelint/stylelint) from 15.7.0 to 15.8.0.
- [Release notes](https://github.com/stylelint/stylelint/releases)
- [Changelog](https://github.com/stylelint/stylelint/blob/main/CHANGELOG.md)
- [Commits](stylelint/stylelint@15.7.0...15.8.0)

---
updated-dependencies:
- dependency-name: stylelint
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

src/Costellobot/package.json

@@ -34,7 +34,7 @@
     "moment": "^2.29.4",
     "prettier": "^2.8.8",
     "style-loader": "^3.3.3",
-    "stylelint": "^15.7.0",
+    "stylelint": "^15.8.0",
     "stylelint-config-standard": "^33.0.0",
     "ts-jest": "^28.0.8",
     "ts-loader": "^9.4.3",