Added animeAiredString property to Anime model

[ToshY]

Related to #486, following comment.

@irfan-dahir Related to this issue, there currently is no property in the Anime model which allows to get the raw airdate string. So I would suggest adding a property there, which can use the the getAnimeAiredString from the AnimeParser. If you're okay with that, I can make the PR.

[irfan-dahir]

Hi, you can get raw airdate by typecasting string to the DateRange object

It's returned like that in the RESTAPI as well:
https://github.com/jikan-me/jikan-rest/blob/16560d3634c6a9116ad7234985aa4e84a11bd683/app/Providers/SerializerFactory.php#L69

'string' => (string)$obj,

In this case you'd have to typecast the following property when getting it:

jikan/src/Model/Anime/Anime.php

Line 97 in ff42009

private DateRange $aired;

(string) $anime->getAired()

[ToshY]

Totally missed that. Thanks @irfan-dahir !