Add link to desktop releases

[Miepee]

I was initially under the impression that cinny was only available as a web client.
The site should add a link to the downloads of the desktop client, in order to show that desktop versions are indeed available.

[br4yd]

I just created a PR for adding that button, because I thought the same.

#9

[chrisdedman]

Bump this. I think it would make it easier for people to get to the desktop client when coming from Cinny website directly rather than matrix.