Add integration for RestSharp Client

Reference: https://restsharp.dev/
Docs: https://nbomber.com/docs/protocols/http/restsharp

API Example:
```csharp
Task<Response<RestResponse>> SendPatch(RestRequest request)
Task<Response<TResponse>> SendPatch<TResponse>(RestRequest request)

Task<Response<TResponse>> SendPut<TResponse>(RestRequest request)
```

- add example of usage
- update documentation with examples under HTTP