Bump @primer/css from 12.3.1 to 12.6.0

[Security] Bump lodash from 4.17.11 to 4.17.15

Bump stylelint-config-primer from 7.0.0 to 7.0.1

Bump stylelint from 10.0.1 to 10.1.0

Search improvement branch

Content footer

Bumps [@primer/css](https://github.com/primer/css) from 12.3.1 to 12.6.0.
- [Release notes](https://github.com/primer/css/releases)
- [Changelog](https://github.com/primer/css/blob/master/CHANGELOG.md)
- [Commits](https://github.com/primer/css/compare/v12.3.1...v12.6.0

)

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

Fixing some Rouge styles for better JavaScript readability

Optimized nav generation

Make sure `baseurl` is appended to the logo href

Fix jekyll highlight tag styles

Replaced old script for analytics with gtag

Modified the google analytics code to match the new tags used by GA

Publish to RubyGems and GPR on release

Added GH Actions CI and removed Travis.

Bumps [lodash](https://github.com/lodash/lodash) from 4.17.11 to 4.17.15. **This update includes security fixes.**
- [Release notes](https://github.com/lodash/lodash/releases)
- [Commits](https://github.com/lodash/lodash/compare/4.17.11...4.17.15

)

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