使用r gt包，我如何在表体中打印一个简单的上标

install.packages("gt")

library(gt)
my_table <- gt()

my_table <- my_table %>%
  tab_header(title = "My Table") %>%
  tab_body(data = my_data)

superscript_text <- expression("X"^"2")

my_table <- my_table %>%
  fmt_text(
    columns = vars(column_name),
    rows = vars(row_name),
    formatter = function(x) {
      fmt <- fmt_text(
        style = cells_text(
          weight = "bold",
          color = "red"
        )
      )
      fmt(x)
    }
  )