Add support for Google Snippets

[ashawley]

I predict the odds of getting your site featured as a snippet as low, so this may not be high priority.

https://support.google.com/websearch/answer/9351707

I guess it is enabled by default?

https://support.google.com/webmasters/answer/6229325

Maybe we could introduce a config that defaults to on, but if false a meta tag for nosnippet is added:

https://support.google.com/webmasters/answer/79812