How to include external css file of a shiny app into flexdashboard

How can I include a external css of a shiny app into the flexdashboard. I have tried putting css file in the YAML header but that didn't work

The style.css is inside www directory

style.css

```
p{
  
  font-size:100px
}
```

dashboard.rmd

```
---
title: 'Dashboard Like a Boss'
output: 
  flexdashboard::flex_dashboard:
    vertical_layout: scroll
    orientation: rows
    runtime: shiny
    css: style.css
---

```{r}
ui <- fluidPage(
  tags$head(tags$link(rel = "stylesheet", href = "style.css")),
  tags$p("Hello, world!")
)

server <- function(input, output, session) {
}
shinyApp(ui, server)

```

In the dashboard, the styling doesn't work, but when the shiny app is run in a separate file (e.g., app.R), the styling works.

Output of flexdasboard:

Output of app.R

I have found a way to use styling for the Shiny App inside flexdashboard. By defining a variable (css in this case) and using tags$style(HTML(css)) within the UI section, you can apply custom styles to the elements in your Shiny App

css <- '
p{
  font-size:100px;
}
'

ui <- fluidPage(
  tags$head(tags$style(HTML(css))),
  tags$p("Hello, world!")
)

server <- function(input, output, session) {
}
shinyApp(ui, server)

Now when I run the document the the flexdashboard display with the style. Even though this won't be the best approach but works for now. Other answers are also welcome