Add RainDragon provider logo #10

Hi @madeburo,

RainDragon was added in #8, and the provider page at https://openmodels.run/providers/raindragon is live. It currently shows the placeholder "R" because /logos/raindragon.svg returns 404.

I've attached our logo as a single-color SVG using currentColor, so it matches the other provider logos. Could you add it as raindragon.svg?

This follows up on my comment on #8.

Thanks!