Changes of version 27.0.0

• [Breaking] Variants for π, τ and « are inserted into the main tag sequence. As a consequence, variant features after them have the tags changed.
• [Breaking] Reordered variants of Eszet.
• [Breaking] Change of variant names:
  • upper-r.straight-motion-serifed → upper-r.straight-top-left-serifed
  • upper-r.curly-motion-serifed → upper-r.curly-top-left-serifed
  • upper-r.standing-motion-serifed → upper-r.standing-top-left-serifed
  • upper-r.straight-open-motion-serifed → upper-r.straight-open-top-left-serifed
  • upper-r.curly-open-motion-serifed → upper-r.curly-open-top-left-serifed
  • upper-r.standing-open-motion-serifed → upper-r.standing-open-top-left-serifed
• Add characters:
  • COMBINING RING OVERLAY (U+20D8).
• Add bottom-right and top-left bottom-right serifed variants of R.
• Add bottom-left motion serifed variants of Cyrillic Ya (Я,я).
• Add cursive variants for Cyrillic Capital/Small Zhe (Ж,ж) (#1762).
• Allow R Rotunda (U+A75A, U+A75B) and Indian Rupee Sign (U+20B9) to have a bottom-right serif.
• Add OpenType zero feature (#1966).
• Fix broken geometry of U+AB3A under condensed width.
• Improve bowl shape of Latin Phi (U+0278).
• Fix dot radius of COMBINING THREE DOTS ABOVE (U+20DB), COMBINING FOUR DOTS ABOVE (U+20DC), and COMBINING TRIPLE UNDERDOT (U+20D8).