add save() and saveBlob() methods to SoundFile. Move .wav conversion to helpers.js

[therewasaguy]

• move .wav conversion from p5.SoundRecorder to helpers module
• add save and saveBlob method to SoundFile
• document the global saveSound method (it was listed under p5.SoundRecorder but is actually part of p5.prototype)
• p5.SoundFile's saveBlob method can probably replace the global saveSoundAsBlob added in Added saveSoundToBlob() to soundRecorder.js #312 —@wahengchang does this sound like a good approach to you?

[wahengchang]

I think most of the users have the needs of sound preview, sound synthesis or wave visualization. so I think we need the blob url for preview sound, and the blob object to manipulate sound:

• saveFile() // as savefile() p5.sound.js already have
• getBlob() // return a blob object, which is going to use to upload file (may be S3, or google cloud)
• getBlobUrl() . // temporary usage, such as sound preview, sound synthesis, or preview sound wave

getBlob()

  p5.SoundFile.prototype.getBlob = function() {
    const dataView = convertToWav(this.buffer);
   return new Blob([dataView], { type: 'audio/wav' })
  }

getBlobUrl()

  p5.SoundFile.prototype.getBlobUrl = function() {
    const dataView = convertToWav(this.buffer);
    const audioBlob = new Blob([dataView], { type: 'audio/wav' });
    return URL.createObjectURL(audioBlob);
  }

[therewasaguy]

Thank you @wahengchang! I like getBlob that's a better name than saveBlob. I wonder if it is really necessary to have getBlobUrl if the audio is already in a SoundFile, maybe we can let users do that with URL.createObjectURL on their own if/as needed?

[wahengchang]

agree, getBlob() is good enough !