UI - Add UI options tab and setting to disable opening diff in a new tab (#3071)

changedetectionio/model/App.py

@@ -60,6 +60,9 @@ class model(dict):
                     'webdriver_delay': None , # Extra delay in seconds before extracting text
                     'tags': {}, #@todo use Tag.model initialisers
                     'timezone': None, # Default IANA timezone name
+                    'ui': {
+                        'open_diff_in_new_tab': True,
+                    },
                 }
             }
         }