Fix ol on index

Update readme

rename master -> main

Update to new repo path

v0.3.3

2019 replaced by 2020 in line 94.

Add custom header and footer include files

Bump stylelint-config-primer from 9.0.0 to 9.2.1

Limit the effect of `nav_exclude` to the main navigation

Bump stylelint from 13.6.1 to 13.7.2

Bump @primer/css from 15.1.0 to 15.2.0

Bump prettier from 2.1.1 to 2.1.2

Update normalize.scss

Update code.scss

Fix list alignment

Bumps [stylelint-config-primer](https://github.com/primer/stylelint-config-primer) from 9.0.0 to 9.2.1.
- [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/v9.0.0...v9.2.1

)

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

Resolve #420

- Remove `margin-top` for the first child in various list items, to improve alignment.
- Add examples of lists to `docs/tests/styling`.

Fix #417

- Avoid appearance of dark border around visited code links in Safari.