docs: add comments about skip disabled

Author: deandreamatias

lib/src/form_builder_field_decoration.dart

@@ -36,6 +36,7 @@ class FormBuilderFieldDecorationState<F extends FormBuilderFieldDecoration<T>,
   F get widget => super.widget as F;
 
   InputDecoration get decoration => widget.decoration.copyWith(
+        // Read only allow show error to support property skipDisabled
         errorText: widget.enabled || readOnly
             ? widget.decoration.errorText ?? errorText
             : null,

test/src/form_builder_test.dart

@@ -183,7 +183,7 @@ void main() {
 
   group('skipDisabled -', () {
     testWidgets(
-        'Should not show error when field is not enabled and skipDisabled is true',
+        'Should not show error when field is disabled and skipDisabled is true',
         (tester) async {
       const textFieldName = 'text3';
       const errorTextField = 'error text field';
@@ -206,7 +206,7 @@ void main() {
       expect(find.text(errorTextField), findsNothing);
     });
     testWidgets(
-        'Should show error when field is not enabled and skipDisabled is false',
+        'Should show error when field is disabled and skipDisabled is false',
         (tester) async {
       const textFieldName = 'text4';
       const errorTextField = 'error text field';