Add a test for the source code fontsize

[Delivers #63083948]
Issue pull request for branch 63083948-pdf-source-code

[Delivers #63083948](https://www.pivotaltracker.com/story/show/63083948)
[#63083948]

* 63083948-pdf-source-code: (29 commits)
  Issue pull request for branch 63083948-pdf-source-code
  Add a test for the source code fontsize
  Issue pull request for branch working-with-rt-62992896
  Add backwards compatiblility for Rails Tutorial
  Polish
  Issue pull request for branch chapter-toc-62963228
  Properly link chapter-star elements in frontmatter
  Link chapter-star elements properly
  Fix an EPUB validation error
  get to green
  Make anal changes
  Get to green
  Move style files to styles directory
  Add directory constants & remove tmp files
  Move book.yml to config directory
  Move book.yml to config
  Properly mock out the publish! command
  Issue pull request for branch ax-cover-config-62857924
  Remove unneded references to the cover file
  Fix uploader message and cp marketing.yml if necessary
  ...
Bump version number
Merge branch 'stable'
marketing.yml include contact_email / hide_custom_domain_footer
Merge branch 'master' of https://github.com/softcover/softcover
Merge branch 'master' into contact-email
Merge pull request #87 from softcover/contact-email

Contact email in marketing.yml