Add ForEachByRef to iterate over arrays by reference to elements

[takanuva15]

The existing lo.ForEach function makes a copy of every element as it iterates, which is problematic for arrays since that prevents them from being modified.

Example:

type Dummy struct {
	f1 string
}

a := []Dummy{{f1: "Hello"}}
fmt.Println(a)
lo.ForEach(a, func(d Dummy, _ int) {
	d.f1 += ", world!"
})
fmt.Println(a)

Output:

[{Hello}]
[{Hello}]

To resolve this, I would like to add a method ForEachByRef which would pass a ref to each array element in the function callback. With the new function, the above code would look like:

a := []Dummy{{f1: "Hello"}}
lo.ForEach(a, func(d *Dummy, _ int) {
	// etc...

If that sounds fine, can I raise a PR to add this function?