[📖] useConstant is not documented

Suggestion

V2 code:

/**
 * Stores a value which is retained for the lifetime of the component. Subsequent calls to
 * `useConstant` will always return the first value given.
 *
 * If the value is a function, the function is invoked once to calculate the actual value.
 *
 * @public
 */
export const useConstant = <T>(value: (() => T) | T): T => {
  const { val, set } = useSequentialScope<T>();
  if (val != null) {
    return val;
  }
  // Note: We are not using `invoke` here because we don't want to clear the context
  value = isFunction(value) && !isQwikComponent(value) ? value() : value;
  return set(value as T);
};

Note: in V1 it's marked as deprecated but not in V2.

Start by locating the V2 useConstant entry point and compare it with the V1 API documentation, where it is marked deprecated. Document the V2 API and clarify its deprecation status; done when useConstant is covered consistently with the project's other public APIs.