Add `IsSpectator()` check for `EPlayer`

sources/Players/EPlayer.uc

@@ -422,6 +422,19 @@ public final function bool IsAdmin()
     return (GetAdminStatus() != AS_None);
 }
 
+/// Checks if player is a spectator, i.e. observes game without actively
+/// participating.
+public final function bool IsSpectator()
+{
+    local PlayerReplicationInfo myReplicationInfo;
+
+    myReplicationInfo = GetRI();
+    if (myReplicationInfo == none) {
+        return true;
+    }
+    return myReplicationInfo.bOnlySpectator;
+}
+
 /**
  *  Changes admin status of the caller `EPlayer`.
  *  Can only fail if caller `EPlayer` has already disconnected.