Add v2.3 support to TypeScript model README

Follow up of #157

This PR updates the README of the TypeScript model to add v2.3 support.

Author: richfab

models/typescript/README.md

@@ -14,6 +14,7 @@ npm install gbfs-typescript-types --save-dev
 ```
 
 ## Versions
+- v2.3
 - v3.0
 - v3.1-RC
 
@@ -38,4 +39,4 @@ fetch(url).then((systemInformationResponse) => {
         systemInformationData = systemInformationJson.data;
     })
 })
-```
+```