Update conferences.md for CityJS Athens and London Events (#7425)

* Update conferences.md for CityJS Athens and London Events

Dear people, I would really appreciate if you include our community events on your website. It might not be titled as React conferences but it does have a lot of React on it! Thank you it is very much appreciated.

* Update conferences.md

Removed spaces as requested.

Author: arismarko

src/content/community/conferences.md

@@ -20,11 +20,21 @@ April 3 (Reanimated Training) + April 4 (Conference), 2025. Paris, France.
 
 [Website](https://reactnativeconnection.io/) - [X](https://x.com/reactnativeconn) - [Bluesky](https://bsky.app/profile/reactnativeconnect.bsky.social)
 
+### CityJS London 2025 {/*cityjs-london*/}
+April 23 - 25, 2025. In-person in London, UK 
+
+[Website](https://london.cityjsconf.org/) - [Twitter](https://x.com/cityjsconf) -  [Bluesky](https://bsky.app/profile/cityjsconf.bsky.social)
+
 ### App.js Conf 2025 {/*appjs-conf-2025*/}
 May 28 - 30, 2025. In-person in Kraków, Poland + remote
 
 [Website](https://appjs.co) - [Twitter](https://twitter.com/appjsconf)
 
+### CityJS Athens 2025 {/*cityjs-athens*/}
+May 27 - 31, 2025. In-person in Athens, Greece
+
+[Website](https://athens.cityjsconf.org/) - [Twitter](https://x.com/cityjsconf) - [Bluesky](https://bsky.app/profile/cityjsconf.bsky.social)
+
 ### React Summit 2025 {/*react-summit-2025*/}
 June 13 - 17, 2025. In-person in Amsterdam, Netherlands + remote (hybrid event)