Changes of version 18.0.0

• [Breaking] Change the way to control whether notches are added to connected equals and hyphens.
  • Whether notches are added are controlled by variant system (#1537).
  • Added separate variant selectors to control whether to add notches to arrow bars.
• Add support of Unicode Variation Sequence for 0 that adds a slash (#1534).
• Fix shaping of /> in Kitty (#1538).