Changes of version 16.0.0

• [Breaking] Change the mechanism of variants of not-equal ligation (#1400):
  • The "dotted" ligation groups (exeqeq-dotted, eqexeq-dotted, eqexeq-dl-dotted, exeq-dotted) are removed.
  • A character variant, "lig-neq" (feature tag VXAF), is added to control the shape instead.
• Ensure that the middle point between Typo Ascender and Descender lies on the middle of symbols/operators (#1398).