Port to Backdrop CMS

Hi Les Lim
Thank you for creating this module. I have ported it to Backdrop CMS.

You can see it at:

• https://github.com/backdrop-contrib/object_log
• https://backdropcms.org/project/object_log

A corresponding ticket to this is at https://github.com/backdrop-ops/contrib/issues/743

If you'd like to co-maintain the Backdrop version you are very welcome.
Thanks
Martin