Version 0.6.0

Breaking changes

• Author and reviewer information must be given in an explicit format with
  mandatory name with mandatory sub-fields given and family.
  corresponding: true indicates the corresponding author.
  email is optional, except for the corresponding author.
  orcid is optional for all persons.

Other changes

• Add create_report() to interactively create an empty report.
• Add add_report_numbers() to add the DOI, report number, ... to an existing
  report.
• Add add_author() to interactively add an author to an existing report.
• Add validate_doi() to validate a DOI.
  pdf_report(), gitbook() and epub_book() use this function to validate
  the optional DOI when set.