get ready for 1.6.0

[michaelglass]

bumps version to 1.6.0 & updates the changelog

[github-actions]

✅ Bigtest for 8586d30 (run)

Benchmarks:

• RSpec: 15.61% overhead
  • RSpec time: 17.81 seconds
  • ABQ time: 20.59 seconds
• RSpec parallel, 10 runs: max 16.56% overhead
  • min 6.96% overhead
  • standard deviation: 2.94%
• Jest: 7.55% overhead
  • Jest time: 21.073 seconds
  • ABQ time: 22.663 seconds

Fuzz result sizes:

• PASSED

[github-actions]

✅ Bigtest for 24720ae (run)

Benchmarks:

• RSpec: 10.28% overhead
  • RSpec time: 17.71 seconds
  • ABQ time: 19.53 seconds
• RSpec parallel, 10 runs: max 11.63% overhead
  • min 7.68% overhead
  • standard deviation: 1.28%
• Jest: 4.84% overhead
  • Jest time: 21.137 seconds
  • ABQ time: 22.161 seconds

Fuzz result sizes:

• PASSED