[📖] useConstant is not documented

[maiieul]

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.