Agrega funciones de search bar

ContactsApp/ContactsViewController.swift

@@ -148,8 +148,25 @@ extension ContactsViewController: UITableViewDelegate, UITableViewDataSource {
 extension ContactsViewController: UISearchBarDelegate, UISearchDisplayDelegate, UISearchResultsUpdating {
     
     func updateSearchResults(for searchController: UISearchController) {
-        <#code#>
+        
+    }
+    
+    func searchBarTextDidEndEditing(_ searchBar: UISearchBar) {
+        self.searchBar.showsCancelButton = false
     }
     
+    func searchBarTextDidBeginEditing(_ searchBar: UISearchBar) {
+        self.searchBar.showsCancelButton = true
+        self.searchBar.resignFirstResponder()
+    }
+    
+    func searchBarCancelButtonClicked(_ searchBar: UISearchBar) {
+        self.searchBar.text = ""
+        self.searchBarTextDidEndEditing(searchBar)
+        self.searchBar.resignFirstResponder()
+    }
 
+    func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String) {
+        print(searchText)
+    }
 }