- Add info about using prebuild image.
- Add info about using prebuild image.

Thanks to xet7 !

GhassenRjab/wekan,wekan/wekan,libreboard/libreboard,wekan/wekan,GhassenRjab/wekan,wekan/wekan,libreboard/libreboard,wekan/wekan,wekan/wekan,GhassenRjab/wekan