gatsby image preloader bug

[rmnprkrl]

Replicate:

• [x] https://substrate.io/developers/playground/
• [x] reload the page
• [x] while image is loading you can see transparent area becomes black

Fix: there should be now change to the transparent are while loading, you can remove that are from the png and add radius top left and ideally config the image component to load transparent images without black BG

another issue on playground:

[rmnprkrl]

is this line on purpose? I would probably just remove it

[je-boska]

I wasn't sure if it was intentional, will remove it.