Construct a path to a location within an installed or development packageSource:
path_package differs from
system.file() in that it always returns an
error if the package does not exist. It also returns a different error if
the file within the package does not exist.
Name of the package to in which to search
Additional paths appended to the package path by
path_package() also automatically works with packages loaded with devtools
even if the
path_package() call comes from a different package.