addField method
Adds a field to the selectors.
Implementation
@override
void addField(String name) {
final plat = current;
if (plat == null || name.trim().isEmpty) return;
plat.selectorDefaults[name] = [''];
plat.mappingDefaults.putIfAbsent(name, () => name);
configEdited('selectors');
configEdited('mapping');
}