💸 add sponsor (#5156)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

Author: nlohmann

README.md

@@ -81,6 +81,7 @@ You can sponsor this library at [GitHub Sponsors](https://github.com/sponsors/nl
 - [Martti Laine](https://github.com/codeclown)
 - [Paul Harrington](https://github.com/phrrngtn)
 - [Mercedes-Benz Group](https://github.com/mercedes-benz)
+- [Ryan McCaffery](https://github.com/mccaffers)
 
 ### :label: Named Sponsors