error[preamble-author]: authors in the preamble must match the expected format
 --> input.md:5:8
  |
5 | author: John Doe @johndoe)
  |        ^^^^^^^^^^^^^^^^^^^ unrecognized author
  |
  = help: Try `Random J. User (@username) <test@example.com>` for an author with a GitHub username plus email.
  = help: Try `Random J. User (@username)` for an author with a GitHub username.
  = help: Try `Random J. User <test@example.com>` for an author with an email.
  = help: Try `Random J. User` for an author without contact information.
error[preamble-author]: preamble header `author` must contain at least one GitHub username
 --> input.md
  |
5 | author: John Doe @johndoe)
  |