gdoc(reference_docx = NULL, token = gd_auth(), browse = NULL, keep_md = FALSE, clean_supporting = TRUE)gd_auth() will load a
previously cached token from .httr-oauth, if available and still
valid. Otherwise, gd_auth() will initiate the browser dance
to obtain and cache a new token, which requires an interactive()
session. gd_auth() can be called explicitly to prepare for
non-interactive() use, such as via the "Knit" button in RStudio.