v0.23.7: Release 0.23.7: recorded voice-overs (#43)

Added

• Voice-overs you recorded yourself: voice("…").recording("vo/intro.wav")
  plays the file instead of calling a speech provider, and the line lasts as
  long as the file. oxframe transcribe vo/intro.wav (oxframe-cli) times
  its words with whisper.cpp on your machine and writes
  vo/intro.words.json, so line.at_word("…") and .caption() follow the
  recording. Without that file the words are spread over its length.