Experimental - Add "event handler" code snippets

Add new code snippets bellow:

• eh (Event Handler)
• seh (Static Event Handler)

// Enter "eh [Tab]", then... 
private void MyMethod(object sender, EventArgs e)
{
    throw new NotImplementedException();
}

// Enter "seh [Tab]", then... 
private static void MyMethod(object sender, EventArgs e)
{
    throw new NotImplementedException();
}