Changes of version 20.0.0

• [Breaking] The ligation sets are now more fine grained to support languages with limited set of ligations (like C++) (#1555).
• Add characters:
  • COMBINING CYRILLIC LETTER UKRAINIAN IE (U+A674) ... COMBINING CYRILLIC LETTER OMEGA (U+A67B).
  • MODIFIER LETTER CYRILLIC HARD SIGN (U+A69C) ... COMBINING CYRILLIC LETTER IOTIFIED E (U+A69F).
  • MODIFIER LETTER CYRILLIC SMALL A (U+1E030) ... MODIFIER LETTER CYRILLIC SMALL YU (U+1E049).
  • MODIFIER LETTER CYRILLIC SMALL SCHWA (U+1E04B) ... MODIFIER LETTER CYRILLIC SMALL ES WITH DESCENDER (U+1E06B).
  • MODIFIER LETTER CYRILLIC SMALL STRAIGHT U WITH STROKE (U+1E06D).
  • COMBINING CYRILLIC SMALL LETTER BYELORUSSIAN-UKRAINIAN I (U+1E08F).
• Add variants for partial differential symbol (#1503).
• Prevent pathological geometry produced in phonetic ligatures (#1562, #1565, #1566, #1568, #1569, # 1570, #1571).
• Improve shape of Cyrillic Yat (#1573).