Adicionar metadados de acessibilidade nas páginas dos livros

[amandasramalho]

Mais detalhes em:
Guidelines: https://www.w3.org/publishing/a11y/metadata-display-guide/guidelines/
EPUB techniques: https://www.w3.org/publishing/a11y/metadata-display-guide/techniques/epub/
ONIX techniques: https://www.w3.org/publishing/a11y/metadata-display-guide/techniques/onix/