Add retrospring

README.md

@@ -337,6 +337,8 @@ Emoji's for each entry provide additional information on project status:
 
 * :heavy_check_mark: [**Ocelot Social**](https://github.com/Ocelot-Social-Community/Ocelot-Social): Free and open-source social network for active citizenship. `MIT, Javascript`
 
+* [**retrospring**](https://github.com/Retrospring/retrospring) ([site](https://retrospring.net/), [Fedi account](https://fosstodon.org/@retrospring)): Q&A based social network. Ask questions, give answers and learn more about your friends. `AGPL-3.0, Ruby`
+
 * [**Smartlike**](https://github.com/smartlike-org/smartlike) ([site](https://smartlike.org/), [Fedi account](https://mastodon.social/@vadim_frolov)): A free non-profit decentralized donation processor with a focus on freedom, privacy and efficiency. `AGPL-3.0, Rust`
 
 * :ghost: [**Agora**](https://github.com/scenaristeur/agora): [Home page](https://scenaristeur.github.io/agora),  POC to use ActivityPub on top of the Solid Platform. - developed by [@spoggy@mstdn.fr](https://mstdn.fr/@spoggy). Latest commit - June 2020