Add readme

Closes #3460887

README.md

-Views Reference Extras
+# Views Reference Extras
+
+This module is for more contributed features extending 
+[Views Reference Field](https://www.drupal.org/project/viewsreference) allowing that module
+to be focused on the core functionality and be kept simple.
+
+## Features
+For now this module has only one feature:
+
+1. **Handling complex Views Reference field configurations**
+
+   Views Reference Field configurations that have many options - like control of which options are shown in a long list
+   of terms - can result in 414 errors. Install this module to extend the compression provided in #3396530: Views
+   reference results in 414 if many options set and ajax used to reload the settings from the entity rather than passing 
+   all settings in the query string.
+
+## Post-Installation
+No change is needed. The module automatically enables the above feature. If multiple features are eventually added, an
+interface for opting in to features will be set up and an upgrade hook to maintain the status quo will be in place (ie,
+this first feature will remain enabled on new sites). If you are still seeing this message, you do not need to take any
+action other than enabling the module.
+
+## Supporting organizations:
+[Soapbox](https://designbysoapbox.com/) - Original development and maintenance.
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