Change lightBoxAdditionalProps relvant props

Thanks to @choozn we fix an issue where some props from react-image-lightbox are not relevant as props to the this library.

These properties are not available to send as additional props (because we already using them internally):
mainSrc, nextSrc, prevSrc, onCloseRequest, onMovePrevRequest, onMoveNextRequest
If you want to pass imageTitle or imageCaption you can pass that via the img props.

I added this section to the readme under Using Lightbox.