[PATCH wayland-web] Mention GammaRay in the tools page

[darxus at chaosreigns.com]

On 08/17, Jonas Ådahl wrote:
> Is half a megabyte really a big deal for wayland-web? I find it more
> reasonable to just provide the full resolution image instead of relying
> on the URL to the external image never changing.

I think I'd only host a thumbnail on the wayland site, only link to the
gammaray page, and let people find the screenshots through that page.