Sample add fix C# MetroMessageBox

[mohamedosama914]

add MetroMessageBox

Fix 

private void Form1_FormClosing(object sender, FormClosingEventArgs e)
 {
 // MetroMessageBox.Show(this, "This is a sample Cancel  MetroMessagebox `Yes`, `No` and `Cancel` button", "MetroMessagebox", MessageBoxButtons.YesNoCancel, MessageBoxIcon.Question);
 }

---

   DialogResult dr = MessageBox.Show(this, " (Application Yes Exit) Button - Yes  |  (Application No Exit) Button + No ", "Application CefSharp Web Browser", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
            if (dr == DialogResult.Yes)
                {
                //  Cef.Shutdown();
                }
            else
                {

                // Application.Exit();
                // cancel the closure of the form.
                e.Cancel = true;

                }