Add alternatives

README.md

@@ -1,2 +1,6 @@
-# open-source-meetup-alternatives
-open-source alternatives to Meetup
+# Open-Source Alternatives to Meetup
+
+- [GetTogether](https://gettogether.community/) ([Source](https://github.com/GetTogetherComm/GetTogether))
+- [attendize](https://www.attendize.com/) ([Source](https://github.com/Attendize/Attendize))
+- [Agorakit](https://agorakit.org/) ([Source](https://github.com/philippejadin/agorakit))
+- [Mobilizon](https://joinmobilizon.org/en/) ([Source](https://framagit.org/framasoft/mobilizon/))