nitdoc: Include the attributes by default.

Signed-off-by: Jean-Christophe Beaupré <jcbrinfo@users.noreply.github.com>
nitdoc: Update the manpage.

Signed-off-by: Jean-Christophe Beaupré <jcbrinfo@users.noreply.github.com>
nitdoc: Add tests with attributes.

Signed-off-by: Jean-Christophe Beaupré <jcbrinfo@users.noreply.github.com>
nitdoc: Display attribute types.

Signed-off-by: Jean-Christophe Beaupré <jcbrinfo@users.noreply.github.com>