Add support for submission to the latest AtCoder contests

[subdiox]

Description

As-is

• When Ex is used as an alphabet of the hardest problem:
  • Character.init caused a crash when a user tried to submit the code, which was missing in Add support for current AtCoder #2.
  • Users couldn't submit their code, because h is used as an ID of the problem.
    (ex: https://atcoder.jp/contests/abc308/tasks/abc308_h)
• Because AtCoder changed the language ID of Swift (4055 -> 5014), users couldn't submit their code.

To-be

Added support for submission to the latest AtCoder contests:

• Replaced all the Character usages with String.
• Users can submit their code even if the alphabet of the problem is Ex, by fetching the problem info every time.
• Users can submit their code, by guessing language ID every time.

Tests by the developer

• Tested that I can submit my code for abc308 problems by running accs submit d.
• Tested that I can submit my code for abc308 problems by running accs submit ex or accs submit Ex.

[ShotaKashihara]

@subdiox Sorry for the late response and thank you for the your contributions. LGTM. I will release this update soon. Thank you again.

[ShotaKashihara]

accs 1.0.16 has been published and can be updated using brew now. Thank you so much!