Support sending voice messages

[MinnDevelopment]

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Changes

• Internal code
• Library interface (affecting end-user code)
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Closes Issue: NaN

Description

This adds support for sending voice messages.

Example

channel.sendFiles(
  FileUpload.fromData(audioFile)
    .asVoiceMessage(MediaType.parse("audio/ogg"), waveform, 10.5)
).queue();

The waveform must be a low frequency sampling of the audio file, with at most 256 samples.