Fix blank_lines var to blanklines in config.yml

This reverts commit 7220197a.

Change button copy on theme preview

Search config

Added documentation for `search_tokenizer_separator`.

[Security] Bump mixin-deep from 1.3.1 to 1.3.2

Bump @primer/css from 12.6.0 to 12.7.0

Allow for custom overrides by the user

Fix trailing comma bug in search-data.json

Improvement/site logo

Update nav.html to eliminate generation of undisplayed elements

Improve heading anchors

Recommend using index.md as parent page for sections

Introduces the possibility for a summary in the table of contents

Bumps [@primer/css](https://github.com/primer/css) from 12.6.0 to 12.7.0.
- [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/v12.6.0...v12.7.0

)

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

Mathjax config options added.
`compress_html` config option changed,
Mathjax script loaded by head when `page.mathjax` is truthy.
Documentation and test page added.
See also issue #198.

This reverts commit 50cdf076.

The default is for hyphens to separate tokens in search terms: `gem-based` is equivalent to `gem based`.

This adds `search_tokenizer_separator` as a site configuation option, to support search for hyphenated words.

This reverts commit 13ef1850.

This reverts commit 0cfc0f03.

This reverts commit 8ac545a5.

This reverts commit c282e4b0.

This reverts commit 5d58a663.

This reverts commit 89f79138.

This reverts commit 209ac7be.

Bumps [mixin-deep](https://github.com/jonschlinkert/mixin-deep) from 1.3.1 to 1.3.2. **This update includes a security fix.**
- [Release notes](https://github.com/jonschlinkert/mixin-deep/releases)
- [Commits](https://github.com/jonschlinkert/mixin-deep/compare/1.3.1...1.3.2

)

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