adding readme about version 1 working on rails 5.2

README.md

@@ -86,6 +86,8 @@ If you want to add a Blog functionality to your app take a look at
 
 CMS for Rails 5.1 doesn't have published gem, but you may use [rails 5.1 branch](https://github.com/comfy/comfortable-mexican-sofa/tree/rails5.1) directly.
 
+If you want to use CMS version 1.12 on Rails 5.2 use [1.13 branch](https://github.com/comfy/comfortable-mexican-sofa/tree/1.13) directly.
+
 With Rails 4.2 and 5.0 use gem version [1.12.10](https://rubygems.org/gems/comfortable_mexican_sofa/versions/1.12.10)
 
 With Rails 3.0 use gem version [1.8.5](https://rubygems.org/gems/comfortable_mexican_sofa/versions/1.8.5)