add content cards in bootstrap code example

Example 1: boostrap card

  

    
Card title
    
Card subtitle
    
Some quick example text to build on the card title and make up the bulk of the card's content.
    Card link
    Another link
  

Example 2: responsive card header

  

    Featured
  
  

    
Cras justo odio
    
Dapibus ac facilisis in
    
Vestibulum at eros
  

Example 3: bootsrap card

  
  

    
Card title
    
Some quick example text to build on the card title and make up the bulk of the card's content.
    Go somewhere