Merge multiple stylesheets given in priority order

css_merge(...)

Arguments

...	multiple CSS objects. The order in which these arguments are given reflect the priority of the stylesheets from lowest to highest priority. Later stylesheets (i.e. high priority) will override any styles declared earlier (lower priority)

final cascaded stylesheet

if (FALSE) {
css1 <- read_css("chrome_builtin.css")
css2 <- read_css("this_page.css")
css_merge(css1, css2)
}