updateEditingValue method
Requests that this client update its editing state to the given value.
The new value is treated as user input and thus may subject to input
formatting.
Implementation
@override
void updateEditingValue(TextEditingValue value) {
text = value.text;
selection = value.selection;
dirtyRegion = TextRange(start: 0, end: value.text.length);
dirtyLine = null;
notifyListeners();
}