Add configureawait for the asynchronous operations

Author: sergeylopatyuk

src/Firebase.Auth/FirebaseAuthProvider.cs

@@ -65,8 +65,8 @@ public async Task<User> GetUserAsync(string firebaseToken)
             var responseData = "N/A";
             try
             { 
-                var response = await this.client.PostAsync(new Uri(string.Format(GoogleGetUser, this.authConfig.ApiKey)), new StringContent(content, Encoding.UTF8, "application/json"));
-                responseData = await response.Content.ReadAsStringAsync();
+                var response = await this.client.PostAsync(new Uri(string.Format(GoogleGetUser, this.authConfig.ApiKey)), new StringContent(content, Encoding.UTF8, "application/json")).ConfigureAwait(false);
+                responseData = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
                 response.EnsureSuccessStatusCode();
 
                 var resultJson = JObject.Parse(responseData);