v2.2.1

• Fixed bug in fontmake.instantiator when several designspace rules touch the same glyphs (#689).
• Update requirements:
  • fonttools >= 4.15.0
    https://github.com/fonttools/fonttools/releases/tag/4.15.0
  • glyphsLib >= 5.2.0
    https://github.com/googlefonts/glyphsLib/releases/tag/v5.2.0
  • ufo2ft >= 2.16.0
    https://github.com/googlefonts/ufo2ft/releases/tag/v2.16.0