Add a SliderProperty

lib/src/story.dart

@@ -237,6 +237,28 @@ class DashbookContext {
     );
   }
 
+  double sliderProperty(
+    String name,
+    double defaultValue, {
+    String? tooltipMessage,
+    ControlProperty? visibilityControlProperty,
+  }) {
+    return addProperty(
+      Property<double>.withBuilder(
+        name,
+        defaultValue,
+        tooltipMessage: tooltipMessage,
+        visibilityControlProperty: visibilityControlProperty,
+        builder: (property, onChanged, key) => p.SliderProperty(
+          property: property,
+          onChanged: onChanged,
+          key: key,
+        ),
+      ),
+    );
+
+  }
+
   Color colorProperty(
     String name,
     Color defaultValue, {

lib/src/widgets/property_widgets/properties.dart

@@ -5,4 +5,5 @@ export 'edge_insets_property.dart';
 export 'list_property.dart';
 export 'number_property.dart';
 export 'options_property.dart';
+export 'slider_property.dart';
 export 'text_property.dart';

lib/src/widgets/property_widgets/slider_property.dart

@@ -0,0 +1,38 @@
+import 'package:dashbook/dashbook.dart';
+import 'package:flutter/material.dart';
+
+class SliderProperty extends StatefulWidget {
+  final Property<double> property;
+  final PropertyChanged onChanged;
+
+  const SliderProperty({
+    required this.property,
+    required this.onChanged,
+    super.key,
+  });
+
+  @override
+  State<StatefulWidget> createState() =>
+      SliderPropertyState(property.getValue());
+}
+
+class SliderPropertyState extends State<SliderProperty> {
+  double value;
+  SliderPropertyState(this.value);
+
+  @override
+  Widget build(BuildContext context) {
+    return PropertyScaffold(
+      tooltipMessage: widget.property.tooltipMessage,
+      label: widget.property.name,
+      child: Slider(
+        value: value,
+        onChanged: (newValue) {
+          value = newValue;
+          widget.property.value = newValue;
+          widget.onChanged();
+        },
+      ),
+    );
+  }
+}