Vertical label to the left of table with KableExtra HTML

Question

I'm creating a critical F-table and I need to assign a vertical text lable to the left of my table ("Degrees of freedom denominator"), as a 'side header' for my table instead of the columnname "df". Does anyone know how to do this?

library(knitr)
library(kableExtra)
library(latex2exp)
library(tidyverse)


# F Table

df_num = c(1:10, 20, 30, 40, 50)
df_denom = c(1:10, 12, 15, 20, 30, 40, 50, 60, 120, 200)

F.table = tibble(
  df_num1 = qf(.99, df1=1, df2=df_denom), 
  df_num2 = qf(.99, df1=2, df2=df_denom), 
  df_num3 = qf(.99, df1=3, df2=df_denom), 
  df_num4 = qf(.99, df1=4, df2=df_denom), 
  df_num5 = qf(.99, df1=5, df2=df_denom), 
  df_num6 = qf(.99, df1=6, df2=df_denom), 
  df_num7 = qf(.99, df1=7, df2=df_denom), 
  df_num8 = qf(.99, df1=8, df2=df_denom), 
  df_num9 = qf(.99, df1=9, df2=df_denom), 
  df_num10 = qf(.99, df1=10, df2=df_denom),
  df_num20 = qf(.99, df1=20, df2=df_denom), 
  df_num30 = qf(.99, df1=30, df2=df_denom), 
  df_num40 = qf(.99, df1=40, df2=df_denom), 
  df_num50 = qf(.99, df1=50, df2=df_denom)
)

F.table = F.table %>% 
  mutate(df = df_denom) %>% 
  select(df, everything())


kable(F.table,
      booktabs = TRUE,
      col.names =  c("df", 1:10, 20, 30, 40, 50), 
      escape = FALSE,
      caption = "$F$-verdeling met kritieke waarden voor $\\alpha  = .01$",
      linesep = "",
      align = c('r'),
      digits=2) %>% 
  kable_styling(font_size = 8) %>% 
  column_spec(1, bold = T, border_right = T) %>% 
  add_header_above(c(" " = 1, "Degrees of freedom numerator (noemer)" = 14)) %>% 
  row_spec(0, extra_css = "border-bottom: 1px solid")