Add Plan page

[wdower]

• Similar to Add foundation Normalize page #49 .
• Discuss and link to Vulcan.
• Give brief context on security baselines and why they are important and how they relate to automated content.
• @wdower might have language for this on Gitbook for SAF.

[wdower]

UPDATE: Discusions with stakeholders suggests that this page needs to be more about the Plan capability and less about Vulcan in particular.

• move the existing Plan page to become the actual Vulcan product page
• on the Plan page, replace the Vulcan screenshots with icons vaguely describing the features of a good Plan tool (can just be simple icons for now)
• add the Plan icon above the header for this page and the phrase "
  
  " as a subheader
• update the Lorem Ipsum paragraph to describe the Plan capability generally