Bump stylelint and stylelint-config-gds

Bumps [stylelint](https://github.com/stylelint/stylelint) and [stylelint-config-gds](https://github.com/alphagov/stylelint-config-gds). These dependencies needed to be updated together.

Updates `stylelint` from 14.16.1 to 15.11.0
- [Release notes](https://github.com/stylelint/stylelint/releases)
- [Changelog](https://github.com/stylelint/stylelint/blob/main/CHANGELOG.md)
- [Commits](stylelint/stylelint@14.16.1...15.11.0)

Updates `stylelint-config-gds` from 0.3.0 to 1.0.0
- [Changelog](https://github.com/alphagov/stylelint-config-gds/blob/main/CHANGELOG.md)
- [Commits](alphagov/stylelint-config-gds@0.3.0...1.0.0)

---
updated-dependencies:
- dependency-name: stylelint
  dependency-type: direct:development
  update-type: version-update:semver-major
- dependency-name: stylelint-config-gds
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>