Not default method

[lpatiny]

We prefer not to expose a default method in a package

https://github.com/jobo322/linear-sum-assignment/blob/587088a2c67983e9a5e868a2b27d47f32435ecf2/src/index.ts#L10

This allows to easily add a new method in package without breaking changes

Could you change this (as well as the readme).