* feat: add polynomialRoot function
This is intended as a benchmark for general arithmetic/basic algebra
functionality of mathjs, but was chosen to be something of potential
independent utility as well, worth adding to mathjs in its own right.
Currently ol=nly computes the numerical roots for real or complex
polynomials of degree three or less.
As usual, adds documentation, embedded documentation, tests, TypeScript
declaration, and TypeScript tests.
Also updates doc.test.js to make it easier to specify an array of complex
numbers as the expected output, and comapres with the appropriate fuzz
in such cases.
Finally, adds a benchmark that computes the roots of all cubics with
nonnegative integer coefficients no larger than five.
* doc: fix typo in polynomialRoot embedded docs
Thanks, SamuelTLG
* style: avoid slightly cryptic Boolean flag stand-in
