add headless infinite scroll component to `@w3ui/react-uploads-list`

[travis]

it would be nice to have a headless component that used reload and next from the UploadsListProvider to make it easy for developers to implement an infinite scrolling uploads list.

I think it would look something like:

function SimpleInfiniteScroll(){
  return (
    <UploadsList>
      <InfiniteScrollList/>
    </UploadsList>
  )
}

function Upload({dataCID, carCID, uploadedAt, uploaderDID}){
  return (
    <div>
      {dataCID} was uploaded at {uploadedAt}
    </div>
  )
}

function SimpleInfiniteScroll(){
  return (
    <UploadsList>
      <InfiniteScrollList itemComponent={Upload}/>
    </UploadsList>
  )
}

[travis]

I've assigned this to myself but happy to have someone else take it, just ping me here to talk about it first.