Release v1.6.0

• Issue 267, PR 269 by Khaled Hosny:
  • Use HarfBuzz for extracting outlines from binary fonts
  • Update uharfbuzz to 0.29.0 (which updates HarfBuzz to 5.0.0)
  • Remove FreeType dependency

Practically, this means:

• Support for avar 2
• Support for more than 65536 glyphs in OTF/TTF