Implement BooleanWidget (#466)

* Implement BooleanWidget

* Merge function of addWidget

* Class conversion

* nit

src/utils/type.ts

@@ -0,0 +1,9 @@
+/**
+ * Converts a plain object to a class instance if it is not already an instance of the class.
+ * @param cls The class to convert to
+ * @param obj The object to convert
+ * @returns The class instance
+ */
+export function toClass<P, C>(cls: new (plain: P) => C, obj: P | C): C {
+  return obj instanceof cls ? obj : new cls(obj as P)
+}