Create How To article on skip nav links.

[closes #181, closes #165]
Merge branch 'article_skip_nav_link' of github.com:ckundo/a11yproject.com into ckundo-article_skip_nav_link

* 'article_skip_nav_link' of github.com:ckundo/a11yproject.com:
  Create How To article on skip nav links.