fix(niri): set pdf viewer to firefox

home/niri.nix

@@ -47,4 +47,11 @@
     enable = true;
     settings.program_options.file_manager = "${pkgs.nautilus}/bin/nautilus";
   };
+
+  xdg.mime = {
+    enable = true;
+    defaultApplications = {
+      "application/pdf" = "firefox.desktop";
+    };
+  };
 }