Fix inline doc for Rakefile content

The previous docs would set the `require 'quarto/tasks'` to be inline but because the code was set to be displayed as `ruby` code and no newline was present before the code block, the `ruby` processing command was displayed as text.

This changes the docs from saying `ruby require 'quarto/tasks'` to `require 'quarto/tasks'`

As a result, the display code is no longer inline, but it is syntax highlighted.
Merge pull request #14 from saturnflyer/master

Fix inline doc for Rakefile content