Switch to Github sponsors link

Author: jamesnw

README.md

@@ -130,4 +130,4 @@ and centered on your needs as a developer!
 We display sponsor logos and avatars
 on our [website](https://www.oddbird.net/polyfill/#open-source-sponsors).
 
-[Sponsor OddBird's OSS Work](https://opencollective.com/oddbird-open-source)
+[Sponsor OddBird's OSS Work](https://github.com/sponsors/oddbird)

index.html

@@ -682,7 +682,7 @@ <h2>Sponsor OddBird's OSS Work</h2>
         >.
       </p>
       <a
-        href="https://opencollective.com/oddbird-open-source"
+        href="https://github.com/sponsors/oddbird"
         target="_blank"
         rel="noopener noreferrer"
         >Sponsor OddBird's OSS Work</a