Add attributes to wrapper html generated by wp_nav_menu

Modifying the wrapper for the wp_nav_menu() is customizable with the items_wrap parameter. https://developer.wordpress.org/reference/functions/wp_nav_menu/

The documentation states that the default wrapper is a <ul> element with an ID an CLASS attribute. This can be modified as you wish by modifying the markup passed to the sprintf() function used by wp_nav_menu().

The value for items_wrap is the argument passed for the wrapper. To output a <div> element with a style attribute:

wp_nav_menu( array( 'items_wrap' => '<div style="css here">%3$s</div>' ) );

The %3$s in the example represents the items within the wrapper HTML.