gsheet2post: Auto attach yaml header to md based on 1 input row of df
In collabin/collabin-dev: Automating Post Submission on Collabin

Auto attach yaml header to md based on 1 input row of df

gsheet2post(
  df,
  post_dir_name = NULL,
  lookup_id = collabin:::lookup_lope_id,
  author_yml_dir = "content/author_info/"
)

`df`	A data frame with one row.
`post_dir_name`	String. The name of the directory of the target post. Defaults to `NULL`. In this case, the value of `post_dir_name` will be automatically extracted from the column `shorturl` of the first argument `df`.
`lookup_id`	A function. Defaults to `collabin:::lookup_lope_id`. This function will be used to map the variable `id` in `df` to the name of the directory of the author. The file `content/author_info/id.yml` defines this mapping relationship. The toppest level of the entries in `id.yml` corresponds to the `id` column in the passed-in `df`. The entries `id` under the toppest level entries are the mapped id returned by `collabin:::lookup_lope_id()`.
`author_yml_dir`	String. The path to the directories where `.yml`s of author information are stored.