Add Appflowy to Task Management (#4089)

Co-authored-by: nodiscc <nodiscc@gmail.com>

README.md

@@ -1984,6 +1984,7 @@ _Related: [Monitoring](#monitoring)_
 
 _Related: [Software Development - Project Management](#software-development---project-management), [Ticketing](#ticketing)_
 
+- [AppFlowy](https://appflowy.io/) - With AppFlowy, you can build detailed lists of to-do’s for different projects while tracking the status of each one. Open Source Notion Alternative. ([Source Code](https://github.com/AppFlowy-IO/appflowy)) `AGPL-3.0` `Rust/Dart/Docker`
 - [Focalboard](https://www.focalboard.com/) - Define, organize, track and manage work across individuals and teams (alternative to Trello, Notion, and Asana). ([Source Code](https://github.com/mattermost/focalboard), [Clients](https://www.focalboard.com/download/personal-edition/desktop/)) `MIT/AGPL-3.0/Apache-2.0` `Nodejs/Go`
 - [Kanbana](https://github.com/SrGMC/kanbana) - Create boards to track users and projects from flat markdown files. Forked from Crepido. `MIT` `Nodejs`
 - [Kanboard](https://kanboard.org/) - Simple and open source visual task board. ([Source Code](https://github.com/kanboard/kanboard)) `MIT` `PHP`