Update conferences.md (#5613)

Add Reactathon 2023 to upcoming conferences

Author: dunphyben

content/community/conferences.md

@@ -12,6 +12,10 @@ Do you know of a local React.js conference? Add it here! (Please keep the list c
 
 ## Upcoming Conferences {#upcoming-conferences}
 
+### Reactathon 2023 {#reactathon-2023}
+May 2 - 3, 2023. San Francisco, CA, USA
+
+[Website](https://reactathon.com) - [Twitter](https://twitter.com/reactathon) - [YouTube](https://www.youtube.com/realworldreact)
 
 ### RemixConf 2023 {#remixconf-2023}
 May, 2023. Salt Lake City, UT