Copies the bundled 'quarto-live' extension into dir/_extensions/ so that
Quarto documents in dir can use format: live-html. This is the
non-interactive equivalent of quarto add r-wasm/quarto-live.
Examples
dir <- tempfile()
add_live_extension(dir)
list.files(dir, recursive = TRUE, all.files = TRUE)[1:3]
#> [1] "_extensions/r-wasm/live/_extension.yml"
#> [2] "_extensions/r-wasm/live/_gradethis.qmd"
#> [3] "_extensions/r-wasm/live/_knitr.qmd"
unlink(dir, recursive = TRUE)