Using the endpoint parameter in Whisperkit and downloading CoreML and tokenizer

[lemo366]

Allows users to specify the endpoint via parameters when initializing WhisperKit, thus enabling the download of CoreML models and tokenizers from domestic mirror sites (such as hf-mirror.com).

let endpoints = "https://hf-mirror.com"
let whisperkit = try await WhisperKit(
      model: modelName,
      verbose: true,
      logLevel: .info, 
      prewarm: true,
      load: true,
      download: true,
      endpoint: endpoint
)

[ZachNagengast]

Thanks @lemo366 this looks great! Do the unit tests pass with hf-mirror as the default? Might be worth including at least one test that uses hf-mirror as the endpoint for a simple download.