Add support for r:site:data

[adamjohnson]

Add support for the <r:site:data name="my-name" /> tag. Brand Patterns now uses this for Google Site Verification out of the box (for Google Search Console / Webmaster Tools). Here's the relevant commit from Brand Patterns:

wvuweb/brand-patterns@e662943?w=0

You should be able to clone Brand Patterns and use that theme for testing.

Here's a site key to copy and paste into your mock_data.yml:

site:
  name: "Brand Patterns"
  data:
    google_site_verification: yo-dog

#29 is related to this issue.