feat: support editing the selected image in a modal

[hirasso]

Hi there @ooksanen ! Thank you for this very nice little package. As I was implementing it in one of my projects, I noticed that the "edit" button from native ACF image fields was missing.

I added it back in:

Now one could edit fields that are directly attached to the image, for example:

Another thing I needed to change:

in your repo, there is no script minification tool installed (no package.json), so I couldn't reproduce the minification after I changed some JS and CSS. Anyways, I don't think the minification is necessary, as both the js and css are so small. So I deleted the two minified files and instead enqueued the unminified files directly.

If you decide to merge my PR, I'd be happily be named in the composer.json as contributor.