Update README.md (#765)

Adding Mux as a supporter (we received credits to use their service)

README.md

@@ -320,7 +320,7 @@ We receive in-kind donations from
 [Codemagic](https://codemagic.io/start/), [Linktree](https://linktr.ee),
 [Twilio](https://twilio.org), [algolia](https://www.algolia.com),
 [JetBrains](https://www.jetbrains.com),
-[1Password](https://1password.com/) and
+[1Password](https://1password.com/), [Mux](https://www.mux.com/) and
 [Lineto](https://www.lineto.com). Our tools also leverage other
 open-source technologies, including solutions like
 [FireCMS](https://firecms.co), [Storybook](https://storybook.js.org) and