title: How to add a UIButton on top of UITabBar inside a UITableView
body: <p>Does anybody know how i can create a UIButton (with constraints height: 35, leading: 0, trailing: 0 and bottom space to UITabBar: 0) inside a UITableView that has a bottom spacing of zero to the UITabBar implemented in the UITableViewController?</p>
  
  <p>What i tried so far:</p>
  
  <pre><code>    let btn = UIButton()
      btn.setTitle("Test Button text", for: .normal)
      btn.tintColor = UIColor.white
      btn.backgroundColor = UIColor.darkGray
      self.view.addSubview(btn)
      btn.translatesAutoresizingMaskIntoConstraints = false
      btn.leadingAnchor.constraint(equalTo: self.view.leadingAnchor, constant: 0).isActive = true
      btn.bottomAnchor.constraint(equalTo: self.view.bottomAnchor, constant: 0).isActive = true
      btn.trailingAnchor.constraint(equalTo: self.view.trailingAnchor, constant: 0).isActive = true
      btn.heightAnchor.constraint(equalToConstant: 35).isActive = true
  </code></pre>