thank/acknowlegge sponsors more prominently

[ramcq]

Flathub is receiving $10ks of services from especially Fastly, but also Packet.net (via CNCF http://cncf.io/), Mythic Beasts and Codethink. The current "Acknowledgements" section hidden on the About page with no links, images or text doesn't do nearly enough to appreciate these huge contributions which allow the service to exist. I suggest:

• Add "Sponsors" as a top-level page, and include the "Individual Donors" as a lower heading on this page
• Find a logo image for each company that sponsors, and hyperlink to each one
• Allow space in the design for us to acknowledge what is donated, and if the companies wish to provide a "blurb".
• Put a rotating "Thanks to our sponsors" or something box/badge on the footer of each page, which picks one of the logos to highlight.

Relatedly, we should add the GNOME Foundation as they paid a recent hosting invoice and provide legal advice (and we are hoping for sysadmin support soon), and Scaleway is no longer a sponsor so can be removed.

[jgarciao]

In our presentation at GUADEC we talked about "companies providing services" and "companies donating time". Do you want both of them or only the fist type? If you want them all, should I merge them or keep them separated by type?

What about having a list of companies that, like Scaleway, sponsored in the past? It could be also in the sponsors page in a lower list without logos and maybe even grouped by year