fix: add classes for picture tag in media component

[Tajmirul]

Sometimes I need to add some classes to the picture tag of Media component. in this case I need to do this:

<Media
    resource={content.image}
    className="w-full h-full [&>picture]:w-full"  // <<< follow this
    imgClassName="w-full h-full object-cover"
/>

So I added an additional props pictureClassName for the picture tag. Now I can do this:

<Media
    resource={content.image}
    className="w-full h-full"
    pictureClassName="w-full h-full" // <<< follow this
    imgClassName="w-full h-full object-cover"
/>

NOTE: I've encountered situations where I needed to add classes to the picture tag, not just for w-full h-full. To handle this, I had to update the Media component. I believe this would be a valuable improvement to the Media component.