xyz server as default multiplayer server

core/src/com/unciv/Constants.kt

@@ -80,6 +80,7 @@ object Constants {
     const val uniqueOrDelimiter = "\" OR \""
 
     const val dropboxMultiplayerServer = "Dropbox"
+    const val uncivXyzServer = "https://uncivserver.xyz/"
 
     const val defaultTileset = "HexaRealm"
     const val defaultUnitset = "AbsoluteUnits"