Use 3s timeout for GetUserAgentAsync and updat test

Author: softworkz

src/ElectronNET.API/API/WebContents.cs

@@ -388,7 +388,7 @@ public void SetAudioMuted(bool muted)
     /// Returns string - The user agent for this web page.
     /// </summary>
     /// <returns></returns>
-    public Task<string> GetUserAgentAsync() => InvokeAsync<string>();
+    public Task<string> GetUserAgentAsync() => InvokeAsyncWithTimeout<string>(3000);
 
     /// <summary>
     /// Overrides the user agent for this web page.

src/ElectronNET.IntegrationTests/Tests/WebContentsTests.cs

@@ -178,8 +178,12 @@ public async Task GetSetUserAgent_check()
         {
             ////Skip.If(Environment.GetEnvironmentVariable("GITHUB_RUN_ID") != null && RuntimeInformation.IsOSPlatform(OSPlatform.Windows), "Skipping test on Windows CI.");
 
+            await Task.Delay(1000);
+
             fx.MainWindow.WebContents.SetUserAgent("MyUserAgent/1.0");
+
             await Task.Delay(1000);
+
             var ok = await fx.MainWindow.WebContents.GetUserAgentAsync();
             ok.Should().Be("MyUserAgent/1.0");
         }