docs: link to undocumented JS interface definitions (#3191)

Co-authored-by: Ben Rometsch <[email protected]>

docs/docs/clients/client-side/react.md

@@ -106,6 +106,9 @@ export function MyComponent() {
 useFlags(requiredFlags:string[], requiredTraits?:string[])=> {[key:string]: IFlagsmithTrait  or IFlagsmithFeature}
 ```
 
+You can find the exact definitions of these types
+[in the SDK](https://github.com/Flagsmith/flagsmith-js-client/blob/main/types.d.ts).
+
 ## FlagsmithProvider API Reference
 
 | Property                 |                                                  Description                                                   | Required | Default Value |