Add sponsor logo (#595)

Author: fenollp

.github/sponsors/speakeasy.png

@@ -8,8 +8,14 @@ A [Go](https://golang.org) project for handling [OpenAPI](https://www.openapis.o
 
 Licensed under the [MIT License](./LICENSE).
 
-## Contributors and users
-The project has received pull requests from many people. Thanks to everyone!
+## Contributors, users and sponsors
+The project has received pull requests [from many people](https://github.com/getkin/kin-openapi/graphs/contributors). Thanks to everyone!
+
+Be sure to [give back to this project](https://github.com/sponsors/fenollp) like our sponsors:
+
+<p align="center">
+	<a href="//www.speakeasyapi.dev"><img src=".github/sponsors/speakeasy.png" alt="Speakeasy" height="100px"/></a>
+</p>
 
 Here's some projects that depend on _kin-openapi_:
   * [github.com/Tufin/oasdiff](https://github.com/Tufin/oasdiff) - "A diff tool for OpenAPI Specification 3"