Adding WTW case study to the readme

Readme.md

@@ -35,6 +35,7 @@ We at [Lombiq](https://lombiq.com/) also used this module for the following proj
 - The new [City of Santa Monica website](https://santamonica.gov/) when migrating it from Orchard 1 to Orchard Core ([see case study](https://lombiq.com/blog/helping-the-city-of-santa-monica-with-orchard-core-consulting)).
 - The new [Smithsonian Folkways Recordings website](https://folkways.si.edu/) when migrating it from Orchard 1 to Orchard Core ([see case study](https://lombiq.com/blog/smithsonian-folkways-recordings-now-upgraded-to-orchard-core)).
 - The new [Lombiq website](https://lombiq.com/) when migrating it from Orchard 1 to Orchard Core ([see case study](https://lombiq.com/blog/how-we-renewed-and-migrated-lombiq-com-from-orchard-1-to-orchard-core)).
+- The new client portal for [Willis Towers Watson](https://www.wtwco.com/) ([see case study](https://lombiq.com/blog/lombiqs-journey-with-willis-towers-watsons-client-portal)).
 - It also makes [DotNest, the Orchard SaaS](https://dotnest.com/) better.
 
 Do you want to quickly try out this project and see it in action? Check it out in our [Open-Source Orchard Core Extensions](https://github.com/Lombiq/Open-Source-Orchard-Core-Extensions) full Orchard Core solution and also see our other useful Orchard Core-related open-source projects!