Opal could use a little tweaking

Thanks for adding Opal to the PortableApps library.

I had the chance to give v1.1.0 a try.

I noticed several things:

1. After running it via the PortableApps Platform launcher, and then closing it, it left behind the folder `\.openjfx\cache\20+19\amd64\` along with 55 `.dll` files in the user's data folder. Interestingly, I tested on a machine with an Intel (not AMD) processor. I think all those files are already present within Opal's PortableApp `runtime\bin` folder, so I'm hoping that something can be tweaked so they don't have to get copied on each run (and then deleted afterwards). It would be good to not chew up SSD write cycles more than needed.

2. Opal doesn't remember its window size between runs. I'm not sure if this can be handled within PortableApps, or if this is an upstream issue. I find that on each run, it's desirable to resize its window.

3. In the PortableApps Platform launcher, the Opal icon is completely black. Thus, when using a dark theme, it is invisible.

4. Within Opal, the icons are black on black when using its dark theme. Again, I'm not sure if this can be handled within PortableApps, or if this is an upstream issue. The Nord Dark theme is an available compromise.

Thanks again.