lib: add myself to maintainers

lib/maintainers.nix

···
   olcai = "Erik Timan <[e-mail]>";
   orbitz = "Malcolm Matalka <[e-mail]>";
   osener = "Ozan Sener <[e-mail]>";
+  oxij = "Jan Malakhovski <[e-mail]>";
   page = "Carles Pagès <[e-mail]>";
   paholg = "Paho Lurie-Gregg <[e-mail]>";
   pakhfn = "Fedor Pakhomov <[e-mail]>";