Added responsive formatting and date support.

[iamarnas]

Improved stability.

• Added responsive formatting. List length can be infinity and never fails...

List<List<Standings>> standings;

//.....
standings: (json['standings'] as List)
    ?.map((e) => (e as List)
        ?.map((e) => e == null
            ? null
            : Standings.fromJson(json['standings'] as Map<String, dynamic>))
        ?.toList())
    ?.toList(),
//.....

• Added DateTime support for some popular format as "2020-02-06T14:00:00+00:00".
• Improved type formatting null values was String as default . Now returns as dynamic and more friendly with jsonfiles.
• Sloved lint warning for dashed class names.
• Code cleaning.
• Updated readme.

[hiranthaR]

@iamarnas I am really sorry I missed this :disappointed:

[iamarnas]

@hiranthaR Hi, it's never too late ;) And welcome to the most stable and accurate version. Only left to fix class names to the same named class with different properties to make this extension would work without problems :)