How to add title and caption to leaflet when it is exports to pdf?

I would like to know how to add title above the map and caption below the map, and how to export it to pdf with certain boundaries (ie zoom to certain area).

library(leaflet)
library(mapview)
library(webshot)
m <- leaflet() %>% addTiles()
m  
mapview::mapshot(m, url = "m.html")
webshot::webshot("m.html",   "m.pdf")