Add gtts-cli

[jpenguin]

edge-tts seem more advance than this, but who knows how long it will continue to work. https://github.com/pndurette/gTTS
it doesn't support different voices, just different languages; don't know if worth it or possible; seems to produce mp3s

gtts-cli --all
  af: Afrikaans
  am: Amharic
  ar: Arabic
  bg: Bulgarian
  bn: Bengali
  bs: Bosnian
  ca: Catalan
  cs: Czech
  cy: Welsh
  da: Danish
  de: German
  el: Greek
  en: English
  es: Spanish
  et: Estonian
  eu: Basque
  fi: Finnish
  fr: French
  gl: Galician
  gu: Gujarati
  ha: Hausa
  hi: Hindi
  hr: Croatian
  hu: Hungarian
  id: Indonesian
  is: Icelandic
  it: Italian
  iw: Hebrew
  ja: Japanese
  jw: Javanese
  km: Khmer
  kn: Kannada
  ko: Korean
  la: Latin
  lt: Lithuanian
  lv: Latvian
  ml: Malayalam
  mr: Marathi
  ms: Malay
  my: Myanmar (Burmese)
  ne: Nepali
  nl: Dutch
  no: Norwegian
  pa: Punjabi
  pl: Polish
  pt: Portuguese
  ro: Romanian
  ru: Russian
  si: Sinhala
  sk: Slovak
  sq: Albanian
  sr: Serbian
  su: Sundanese
  sv: Swedish
  sw: Swahili
  ta: Tamil
  te: Telugu
  th: Thai
  tl: Filipino
  tr: Turkish
  uk: Ukrainian
  ur: Urdu
  vi: Vietnamese
  zh-CN: Chinese (Simplified)
  zh-TW: Chinese (Mandarin/Taiwan)
  zh: Chinese (Mandarin)

Examples:
echo "Victor jagt zwölf Boxkämpfer quer über den großen Sylter Deich" | gtts-cli -l de -f - | mpv -
echo "The five boxing wizards jump quickly." | gtts-cli -l en -f - | mpv -
echo "Portez ce vieux whisky au juge blond qui fume" | gtts-cli -l fr -f - | mpv -

[aedocw]

Interesting, I was was not familiar with this. I probably won't have spare time to add this for a while but I'll keep this open to remind me to do it one of these days.