Add preliz to the list of libraries and Aalto and FCAI to the list of sponsors

[aloctavodia]

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📚 Documentation preview 📚: https://arviz-project--59.org.readthedocs.build/en/59/

[OriolAbril]

I have moved Aalto and FCAI to institutional partners and also moved CZI to the list of historical funders as it is now inactive sponsor and has been for 6 months. I have also added light/dark versions of the aalto logo.

While I was doing that I also did some general maintenance, removed twitter and made the list of external links easier to maintain. It was done in raw html to include the rel="me" piece for mastodon validation, so I repeated the mastodon link as hidden in the main page which should hopefully achieve the same result while keeping the list of external links clearly in the index.md page so they are easier to maintain and update.

I also realized I forgot to add @star1327p to the "our team" page when I closed the nomination issue, so I did it now. @star1327p I copied the name as it appears on the GitHub profile but I could have used the name as it appears on Slack. let us know how you prefer to be listed and we'll merge once you approve the PR

[star1327p]

Please add my name as Christine P. Chai. Thanks!