Support for "posts_per_row" parameter for People layout

[voraci0us]

Description

For better integration with the UCF Post List Shortcode, add support for the "posts_per_row" parameter with the People layout.

Why it's Important

Making this request for the Burnett Honors College website, this page in particular. We use the People layout on three other pages as well, which would benefit as well.

Additional context

How the page looks currently (rows are unbalanced):

How the page looks after resizing (we would like it to look this this initially, i.e. "posts_per_row=4"):

No matter how much room the shortcode has to display the space, it always shows 6 people initially: