protonvpn-gui: add rapiteanu as maintainer

Added myself as a maintainer since I've been helping with this package
for some time now and I intend to continue to do so.

pkgs/applications/networking/protonvpn-gui/default.nix

@@ -80,6 +80,9 @@ buildPythonApplication rec {
     license = lib.licenses.gpl3Plus;
     platforms = lib.platforms.linux;
     mainProgram = "protonvpn-app";
-    maintainers = with lib.maintainers; [ sebtm ];
+    maintainers = with lib.maintainers; [
+      sebtm
+      rapiteanu
+    ];
   };
 }