Create the benchmark using phpbench (https://github.com/phpbench/phpbench), a solid and well-maintained tool.

• Add phpbench as requirement (require-dev)
• Add benchmarks for the Initializers (https://numpower.org/api/category/initializers)
• Add benchmarks for the linear algebra methods (https://numpower.org/api/category/linear-algebra)
• Add benchmarks for the arithmetic methods (https://numpower.org/api/category/arithmetics)
• Add benchmarks for sum and products methods (https://numpower.org/api/category/sums-products-differences)