A string representing the desired documentation for the exact
FRED API endpoint. Default is "base", which will open a link to
https://api.stlouisfed.org/docs/fred/.
params
A boolean value. If TRUE, the documentation will be opened at
the "Parameters" section. Default is FALSE.
debug
A boolean value. If TRUE, the documentation is not opened in a
browser and the documentation URL is returned as a string. If FALSE,
documentation is opened in a browser and nothing is returned. Default is
FALSE.