Add sponsorship section

[valencik]

We should have a page that thanks our current sponsors, displays their logos, and provides a link to the open collective site.
(https://opencollective.com/typelevel)

[armanbilge]

Here's how we do it on the Cats landing page.

https://github.com/typelevel/cats/blob/c2b8c1e9b287474722437dd94b05ffc1dc38025a/docs/index.md?plain=1#L32-L66

https://github.com/armanbilge/cats/blob/c2b8c1e9b287474722437dd94b05ffc1dc38025a/docs/js/sponsors.js

[reardonj]

Any thoughts on where this would be? There is a contributing page which is the closest correspondence in content to the Cats site, but is deeply buried compared to it being on the main page of the Cats site.

[jducoeur]

We're starting to discuss doing a deep rewrite of the main TL site using Laika, so we should think about it in that context.

(Really, we need to do at least a cursory information-architecture review of the TL site, and what we want that to look like, with this as a page to add along the way.)