Implement performance benchmarks, rewrite README.md

[iotamale]

Benchmarking

• Added a benchmarking script using mitata.
• Implemented 3 scenarios:
  1. Bulk enqueue/dequeue
  2. Steady state / interleaved
  3. Memory reuse / clear overhead
• Benchmarked vs standard array methods and popular NPM competitors (denque and yocto-queue).

README rewrite

• Consolidated all optimisation related information to a single section.
• Documented the deliberate engineering trade-offs.
• Showcased the new benchmarking data.