add histogram.mjs and histogram becnhmarking

[jayshah1819]

Features

Two binning strategies:

• Even bins: Arithmetic binning for uniform ranges
• Custom bins: Binary search for arbitrary bin edges

Grid-stride loop pattern for processing large inputs
Shared memory optimization for ≤256 bins
Falls back to global atomics for larger bin counts

kernels

Init kernel: zeros output buffer
Sweep kernel: 3-phase execution (init shared mem → process data → merge results)

Benchmarking result (even, custom- trial:20, inputLength: 2^27)