For years, downtowns were the cool place to be. Companies moved their offices to attract urban-minded millennials. Development continues in Kansas City’s downtown, but Johnson County hasn’t conceded. In fact, growth is strong in its office market. In the fourth quarter of 2018, 61 percent of multitenant buildings under construction were in Johnson County, accounting for 383,797 square feet, according to a report from global commercial real estate firm CBRE. In…