Add OSS Sponsorship link to README

README.md

@@ -144,3 +144,10 @@ to group & namespace normal Sass variables meaningfully,
 and [access module variables as a map](https://sass-lang.com/documentation/modules/meta#module-variables).
 By relying on core Sass features,
 we avoid any confusion around the custom token syntax.
+
+______
+### Sponsor OddBird's OSS Work
+
+At OddBird, we love contributing to the languages & tools developers rely on. We're currently working on polyfills for new Popover & Anchor Positioning functionality, as well as CSS specifications for functions, mixins, and responsive typography. Help us keep this work sustainable and centered on your needs as a developer! We display sponsor logos and avatars on our website.
+
+[Sponsor OddBird's OSS Work](https://opencollective.com/oddbird-open-source)