Add file deletion detection, WebKit improvements, and bug fixes

- Add FileExternallyDeletedEvent with UI indicator in tabs for deleted files
- Set minimum height (300px) for editors container
- Add Developer Tools to WebKit context menu
- Fix DnD URI handling when uris list is empty
- Fix buffer replacement using freeze_notify and proper bounds handling
- Move webkit_ui_settings to new path
- Remove <change_me> placeholders from APP_NAME and user config

src/__builtins__.py

@@ -43,7 +43,7 @@ def call_chain_wrapper(fn):
 
 # NOTE: Just reminding myself we can add to builtins two different ways...
 # __builtins__.update({"event_system": Builtins()})
-builtins.APP_NAME          = "<change_me>"
+builtins.APP_NAME          = "<change_me>".replace("<","").replace(">","")
 
 builtins.keybindings       = Keybindings()
 builtins.event_system      = EventSystem()