Add composer.json to set minimal Drush version, drop support for Drush 8 and...
requested to merge issue/migrate_file_to_media-3247728:3247728-drush_command_documentation into 8.x-1.x
Add composer.json to set minimal Drush version, drop support for Drush 8 and update readme to clarify the duplicate file detection command
Closes #3247728