feat: add revealer widget

docs/widgets.md

@@ -182,6 +182,34 @@ label = Label(
 )
 ```
 
+## Revealer
+
+A widget that can reveal its child.
+
+**Properties**
+
+| Property              | Type                                                                                                           | Description                                     |
+| --------------------- | -------------------------------------------------------------------------------------------------------------- | ----------------------------------------------- |
+| `reveal_child`        | `bool`                                                                                                         | Whether the child is revealed or not.           |
+| `transition_duration` | `int`                                                                                                          | The duration of the transition in milliseconds. |
+| `transition_type`     | [`Gtk.RevealerTransitionType`](https://lazka.github.io/pgi-docs/Gtk-3.0/enums.html#Gtk.RevealerTransitionType) | The type of the transition.                     |
+| `child`               | [`Gtk.Widget`](https://lazka.github.io/pgi-docs/index.html#Gtk-3.0/classes/Widget.html#Gtk.Widget)             | The child of the revealer.                      |
+
+**Example**
+
+```python
+from sora.widgets.revealer import Revealer, RevealerProps
+
+revealer = Revealer(
+    RevealerProps(
+        reveal_child=True,
+        transition_duration=500,
+        transition_type=Gtk.RevealerTransitionType.CROSSFADE,
+        child=Label(LabelProps(label="Hello, world!")),
+    ),
+)
+```
+
 ## Slider
 
 A slider widget.

sora/widgets/revealer.py

@@ -0,0 +1,35 @@
+from dataclasses import dataclass
+
+from sora.widgets.base import BaseWidget, BaseWidgetProps
+from sora.widgets.bind import Bindable
+
+from gi.repository import Gtk
+
+
+@dataclass(kw_only=True)
+class RevealerProps(BaseWidgetProps):
+    """
+    Properties for the Revealer widget.
+
+    :param reveal_child: Whether the child is revealed.
+    :param transition_duration: The duration of the transition in milliseconds.
+    :param transition_type: The type of the transition animation.
+    :param child: The child widget.
+    """
+
+    reveal_child: Bindable[bool] = False
+    transition_duration: Bindable[int] = 1000
+    transition_type: Bindable[
+        Gtk.RevealerTransitionType
+    ] = Gtk.RevealerTransitionType.NONE
+    child: Bindable[Gtk.Widget] | None = None
+
+
+class Revealer(BaseWidget(Gtk.Revealer), Gtk.Revealer):
+    def __init__(self, props: RevealerProps):
+        super().__init__(props)
+
+        self._bind_property("reveal_child", props.reveal_child)
+        self._bind_property("transition_duration", props.transition_duration)
+        self._bind_property("transition_type", props.transition_type)
+        self._bind_property("child", props.child)