Add radioplay subdomain to subdomains.json

Author: MichaelOlds

subdomains.json

@@ -84,6 +84,7 @@
     "project-integration": "138.199.207.53",
     "pxl": "heypxl.github.io",
     "random-things-on-internet": "45.14.194.247",
+    "radioplay": "radioplay.pages.dev",
     "raster": "ilwidfr.github.io",
     "reha": "rreha.github.io",
     "rewardify": "nskcheats.github.io",