* Make property names monospace
Property names as monospace would be more fitting to this challenge.
* Add default value for align-items
According to the standard, the default value for align-items, if it is not specified, is stretch.
Source: https://www.w3schools.com/cssref/css3_pr_align-items.asp
* Add monospace font for code elements
These elements need to be in a monospace font.