Add JWT logo image attribution (golang-jwt#161)

README.md

@@ -119,3 +119,5 @@ This library uses descriptive error messages whenever possible. If you are not g
 Documentation can be found [on pkg.go.dev](https://pkg.go.dev/github.com/golang-jwt/jwt).
 
 The command line utility included in this project (cmd/jwt) provides a straightforward example of token creation and parsing as well as a useful tool for debugging your own integration. You'll also find several implementation examples in the documentation.
+
+[golang-jwt](https://github.com/orgs/golang-jwt) incorporates a modified version of the JWT logo, which is distributed under the terms of the [MIT License](https://github.com/jsonwebtoken/jsonwebtoken.github.io/blob/master/LICENSE.txt).