Update IAuthenticator? Authenticator in usage.md (#2151)

* Update usage.md

Conform to updated API

* Update usage.md

Conform the latest API

Author: mavaddat

docs/usage.md

@@ -60,10 +60,10 @@ Now, we need to implement the `GetToken` function in the class:
 
 ```csharp
 async Task<string> GetToken() {
-    var options = new RestClientOptions(_baseUrl);
-    using var client = new RestClient(options) {
+    var options = new RestClientOptions(_baseUrl){
         Authenticator = new HttpBasicAuthenticator(_clientId, _clientSecret),
     };
+    using var client = new RestClient(options);
 
     var request = new RestRequest("oauth2/token")
         .AddParameter("grant_type", "client_credentials");
@@ -107,11 +107,11 @@ public class TwitterClient : ITwitterClient, IDisposable {
     readonly RestClient _client;
 
     public TwitterClient(string apiKey, string apiKeySecret) {
-        var options = new RestClientOptions("https://api.twitter.com/2");
-
-        _client = new RestClient(options) {
+        var options = new RestClientOptions("https://api.twitter.com/2"){
             Authenticator = new TwitterAuthenticator("https://api.twitter.com", apiKey, apiKeySecret)
         };
+
+        _client = new RestClient(options);
     }
 
     public async Task<TwitterUser> GetUser(string user) {