Changes of version 21.0.0

• [Breaking] Added ligation support for Erlang. As a result, ligations groups for less-then-or-equal and greater-than-or-equal symbols are reorganized (#1595).
• Add characters:
  • MEDIUM MATHEMATICAL SPACE (U+205F).
  • MILL SIGN (U+20A5).
  • DONG SIGN (U+20AB).
  • TENGE SIGN (U+20B8).
  • SOM SIGN (U+20C0).
  • EULER CONSTANT (U+2107).
  • SCRUPLE (U+2108).
  • PLANCK CONSTANT OVER TWO PI (U+210F).
  • SQUARE LOZENGE (U+2311).
  • TURNED NOT SIGN (U+2319).
  • SOFTWARE-FUNCTION SYMBOL (U+2394).
  • PLUS SIGN WITH DOT BELOW (U+2A25).
  • MINUS SIGN WITH DOT BELOW (U+2A2A).
  • EQUALS SIGN WITH DOT BELOW (U+2A66).
  • LATIN CAPITAL LETTER H WITH DESCENDER (U+2C67) (#1572).
  • LATIN SMALL LETTER H WITH DESCENDER (U+2C68) (#1572).
  • RING POINT (U+2E30).
  • WORD SEPARATOR MIDDLE DOT (U+2E31).
  • LATIN LETTER SINOLOGICAL DOT (U+A78F).
  • LATIN CAPITAL LETTER N WITH DESCENDER (U+A790) (#1572).
  • LATIN SMALL LETTER N WITH DESCENDER (U+A791) (#1572).
  • LATIN CAPITAL LETTER OMEGA (U+A7B6) (#1572).
  • LATIN SMALL LETTER OMEGA (U+A7B7) (#1572).
  • LATIN CAPITAL LETTER D WITH SHORT STROKE OVERLAY (U+A7C7) (#1572).
  • LATIN SMALL LETTER D WITH SHORT STROKE OVERLAY (U+A7C8) (#1572).
  • LATIN CAPITAL LETTER S WITH SHORT STROKE OVERLAY (U+A7C9) (#1572).
  • LATIN SMALL LETTER S WITH SHORT STROKE OVERLAY (U+A7CA) (#1572).
  • LATIN SMALL LETTER OPEN O WITH STROKE (U+AB3F) (#1572).
• Make ASCII marks (grave, caret, tilde) more significant (#1576).
• Optimize shape for Italic long-dotted-oval zero (#1577).
• Fix ear-cuts of capital Y under Italics (#1578).
• Fix disconnected Cedillas for serifed italic glyphs on heavier weights (#1579).
• Fix disconnected underbars for Abkhasian Che (#1579).
• Fix shape of heavy-weight serifed Latin C With Hook, Epsilons (#1580).
• Fix heavy-weight ampersand's top arc alignment (#1581).
• Fix shape of heavy-weight lowercase r (#1582).
• Optimize shape for Sulzbacher Eszet (#1583).
• Fix missing serifs of Cyrillic Koppa (#1584).
• Fix shape of heavy-weight Rs (#1585).
• Fix shape of Latin Small Letter Y with Hook under heavy weights (#1588, #1589).
• Fix shape of Bashkir Ka under heavy weights (#1590).
• Fix artifacts of certain K-related letters (#1591).
• Optimize shape of small S (#1592).