Version 13.0.0

Changes:

• ⚠️ source code now uses ES6 language features (#156)
• ⚠️ name properties should no longer be relied upon (#157)
• 🎉 significant performance improvements (#151)
• test methods now respect constraints (#145)
• Z.equals now uses structural equality to compare values lacking a fantasy-land/equals implementation (#154)
• internal simplifications (#143, #146, #164)