如何在使用Shiny和Shinydashboard时使图标的大小保持一致？

library(shiny)
library(shinydashboard)

ui <- dashboardPage(
  dashboardHeader(),
  dashboardSidebar(),
  dashboardBody(
    tags$head(
      tags$style(HTML(
        "
        .icon-size {
          font-size: 20px;
        }
        "
      ))
    ),
    fluidRow(
      box(
        width = 6,
        solidHeader = TRUE,
        status = "primary",
        title = "Example Box",
        icon = icon("chart-line", class = "icon-size"),
        "Content"
      )
    )
  )
)

server <- function(input, output) {}

shinyApp(ui, server)