Combine the mkvMerge and ffmpeg variants into single script

[vorwd]

Combine the mkvMerge and ffmpeg variant(s) into a single script and automate the deletion of the original file.

Deletion of $input file requires validation:

• $final_output_file achieves pass criteria parsed from the $input_file and $final_output_file ffprobe .json results
  • define criteria that would ensure premature deletion didn't occur
  • add user input prompt that would indicate if this was something they wanted each time the script was ran (not each loop/file)