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.

v0.2.5 release branch

Bump stylelint-config-primer from 6.0.0 to 7.0.0

Bump @primer/css from 12.2.3 to 12.3.1

Bumps [@primer/css](https://github.com/primer/css) from 12.2.3 to 12.3.1.
- [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/v12.2.3...v12.3.1

)

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

Bumps [stylelint-config-primer](https://github.com/primer/stylelint-config-primer) from 6.0.0 to 7.0.0.
- [Release notes](https://github.com/primer/stylelint-config-primer/releases)
- [Changelog](https://github.com/primer/stylelint-config-primer/blob/master/CHANGELOG.md)
- [Commits](https://github.com/primer/stylelint-config-primer/compare/v6.0.0...v7.0.0

)

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

v0.2.4 release branch

Bump stylelint-config-primer from 3.0.1 to 6.0.0

Bump stylelint from 9.10.1 to 10.0.1

Add SEO and 'lang' param for `_config`

Import custom Sass variable overrides before default variables are defined

Remove unnecessary console.log()

Explain how to use theme locally with GitHub Pages