["Request"] Improve documentation for filtering within list

[n3ziniuka5]

What version are you currently using? 1.2.0

What would you like to see?

OptionalGetter.filter has the following javadoc:

    /**
     * [OptionalGetter] to itself if it satisfies the predicate.
     *
     * Select all the elements which satisfy the predicate.
     *
     * ```kotlin
     * import arrow.optics.Traversal
     * import arrow.optics.Optional
     *
     * val positiveNumbers = Traversal.list<Int>() compose OptionalGetter.filter { it >= 0 }
     *
     * positiveNumbers.getAll(listOf(1, 2, -3, 4, -5)) == listOf(1, 2, 4)
     * ```
     */

The issue I am facing is that Traversal.list<Int>() compose OptionalGetter.filter { it >= 0 } doesn't compile:

ype mismatch: inferred type is OptionalGetter<???, ???> /* = POptionalGetter<???, ???, ???> */ but PTraversal<in Int, out Int, out TypeVariable(C), in TypeVariable(D)> was expected
Type mismatch: inferred type is (???) -> Unit but (???) -> Boolean was expected
Type mismatch: inferred type is Unit but Boolean was expected

At the moment I am struggling to find examples on how to zoom into a particular element in the list. My use-case is a data class A with a property b: List<B>, and given A, I want to make a change to B.someProperty, but only for a list element that satisfies some condition. Help would be appreciated.