v1.8.0

• Add Thai phonemizer using TLTK in the new th extra
  • --data.phoneme_type thai for training; "phoneme_type": "thai" in a voice config for synthesis
  • espeak-ng's Thai voice is a placeholder: its th_dict holds no lexicon, so unspaced Thai is never segmented; the leading vowels เ แ โ ใ ไ are not reordered; and a tone mark deletes the syllable's vowel, collapsing ป่า/ป้า/ป๊า/ป๋า to the same phonemes
  • TLTK does dictionary-based word segmentation and emits a tone digit (1-5) per syllable, in the same style phonemize_chinese uses for Mandarin tones
  • The whole inventory already has ids in the default IPA map, so Thai voices stay compatible with the IPA-based (espeak) warmstart
• Add script/setup --th, and install the th extra in CI so the Thai tests run