Set 'lang' attribute based on the locale of the page #95
Description
Currently, an AsciiDoc document cannot conveniently obtain current_page.options[:locale] set by the I18n extension, and it seems natural for it to be reflected in the 'lang' attribute since its standard (and used by some converters).
It would be better if we are able to specify translation strings based on the locale, either obtaining them from the I18n extension or set from configuration or data files.