docs(readme): add Modem sponsor block (#209)

Author: benvinegar

README.md

@@ -161,6 +161,18 @@ Each example includes the exact command to run from the repository root.
 
 For source setup, tests, packaging checks, and repo architecture, see [CONTRIBUTING.md](CONTRIBUTING.md).
 
+## Sponsor
+
+Sponsored by [Modem](https://modem.dev?utm_source=github&utm_medium=oss&utm_campaign=hunk).
+
+<a href="https://modem.dev?utm_source=github&utm_medium=oss&utm_campaign=hunk">
+  <picture>
+    <source media="(prefers-color-scheme: dark)" srcset="https://modem.dev/images/logo/svg/modem-combined-white.svg">
+    <source media="(prefers-color-scheme: light)" srcset="https://modem.dev/images/logo/svg/modem-combined-black.svg">
+    <img src="https://modem.dev/images/logo/svg/modem-combined-black.svg" alt="Modem" width="220">
+  </picture>
+</a>
+
 ## License
 
 [MIT](LICENSE)