ForEach slice modify(optional)

[ethahae]

Maybe ForEach can modify elements is a good idea, I don't know. But some real scene need this feature.
Someone prefers
results := []int{}
funk.ForEach([]int{1,2,3}, func(x int){ results = append(results, x * 2})
resultsAnother := []int{}
funk.ForEach(results, func(x int){ resultsAnother = append(resultsAnother, x * 3})
but someone prefers
data := []int{1,2,3}
funk.ForEach(data, func(x *int){ *x = *x * 2})
funk.ForEach(data, func(x *int){ *x = *x * 3})

go's map cannot be modified by the reflect value. reflect#Value#MapIndex#CanSet is false. Use SetMapIndex is a way, but it need a func(x *any) any as predicate func breaks go-funk's consensual, so I left it.