Document the Crossover functions a bit better with examples

[JensRantil]

For example, https://pkg.go.dev/github.com/MaxHalford/eaopt#CrossERX states

CrossERX (Edge Recombination Crossover).

I don't know what that means. Would be nice with an example or link to somewhere on the Internet that explains this.

The same type of feedback applies to many of the other Cross* functions.

[MaxHalford]

Hey there. I don't have time to devote to this project, sadly.

[JensRantil]

No worries. Do you think you could share where you learned about the crossover functions? Any book? Course? Something else? I might be able to contribute this myself. I find this project very interesting.

[MaxHalford]

So it's been a while. There was a time where I was doing a lot of evolutionary stuff. I mostly got this knowledge from reading obscure papers. But at the time I was a university student, so I wouldn't as good as now at taking notes. So no sorry I don't have a lot of references. I think you can find a lot of results online if you Google stuff like "Edge Recombination Crossover". I'm sorry I don't have a better answer :(