includes language language as part of the output path extension

[drzraf]

Using auto-language + output-dir, a subtitle named after the original is created (at the same location independently of the detection options)

whisper-ctranslate2/src/whisper_ctranslate2/writers.py

Lines 41 to 43 in 4ecf254

	output_path = os.path.join(
	self.output_dir, audio_basename + "." + self.extension
	)

In situation where language can't predicted, a user could legitimately prefer subtitles to be created like <filename>.<detected-language>.srt (foo.de.srt, foo.en.srt) according to the language ctranslate2 detected.
This would avoid subsequent override later on when --language=... is passed and keep track of the language when operating over a batch of files from different sources.

I suggest to include an option to handle this scenario.