update isso homepage link

- ref. https://github.com/awesome-selfhosted/awesome-selfhosted/issues/2266

README.md

@@ -532,7 +532,7 @@ Simple deployment of [E-mail](https://en.wikipedia.org/wiki/Email) servers, e.g.
 - [GoToSocial](https://github.com/superseriousbusiness/gotosocial) - ActivityPub federated social network server implementing the Mastodon client API. `AGPL-3.0` `Docker/Go`
 - [Hubzilla](https://hubzilla.org) - Decentralized identity, privacy, publishing, sharing, cloud storage, and communications/social platform. ([Source Code](https://framagit.org/hubzilla/core)) `MIT` `PHP`
 - [HumHub](https://www.humhub.org/) - Flexible kit for private social networks. ([Source Code](https://github.com/humhub/humhub)) `AGPL-3.0` `PHP`
-- [Isso](https://posativ.org/isso/) - Lightweight commenting server written in Python and Javascript. It aims to be a drop-in replacement for Disqus. ([Source Code](https://github.com/posativ/isso)) `MIT` `Python/Docker`
+- [Isso](https://isso-comments.de/) - Lightweight commenting server written in Python and Javascript. It aims to be a drop-in replacement for Disqus. ([Source Code](https://github.com/posativ/isso)) `MIT` `Python/Docker`
 - [kbin](https://kbin.pub/) - Federated content aggregator and microblogging platform. ([Source Code](https://github.com/ernestwisniewski/kbin)) `AGPL-3.0` `PHP/Nodejs/Docker`
 - [Lemmy](https://join-lemmy.org/) - A link aggregator / reddit clone for the fediverse. Reddit alternative built in Rust. ([Source Code](https://github.com/LemmyNet/lemmy)) `AGPL-3.0` `Rust`
 - [Libreddit](https://github.com/spikecodes/libreddit/) `⚠` - Private front-end for Reddit written in Rust. `AGPL-3.0` `Rust`