Add donorbox.org to donations.md

Author: theodorosploumis

donations.md

@@ -4,7 +4,7 @@
 
 - [GitHub Sponsors](https://github.com/sponsors)
 - [Open Collective](https://opencollective.com)
-- [Open Source Pledge](https://opensourcepledge.com/)
+- [Open Source Pledge](https://opensourcepledge.com)
 - [thanks.dev](https://thanks.dev)
 - [patreon.com](https://www.patreon.com)
 - [Buy Me a Coffee](https://www.buymeacoffee.com)
@@ -15,6 +15,7 @@
 - [Open Source Collective](https://www.oscollective.org)
 - [OSS.Fund](https://www.oss.fund)
 - [PayPal.Me](https://www.paypal.me)
+- [donorbox.org/](https://donorbox.org)
 
 ## Software specific