adds splitting audio file cookbook

[MerlynTheWizard]

Adds a cookbook on how to split audio files that are too big for Salad Transcription API to files of 2.5 hours or less.

[mgorkii-nlplogix]

Few comments:

1. You are using "input_file" vaiable in split_audio function, but it is not passed into it as an argument. Should be changed to "file_path"
2. "MP3 and MP4 files are compatible, but will always convert to MP3."
   For mp4 you will also need to extract audio first with FFmpeg
3. You need to split "input_file" to remove file format before you do this:
   f"{input_file}segment{i//segment_length + 1}.mp3", otherwise you will get somthing like that: audio.mp3_segment_1.mp3
   Need to add something like that: os.path.splitext(os.path.basename(file_path))[0]