Changed bootloader mount point from /boot/efi to /boot & added yubikey.nix config

nixos/yubikey.nix

@@ -0,0 +1,29 @@
+{ pkgs, ...}:
+
+{
+  services.udev.packages = [ pkgs.yubikey-personalization ];
+
+  programs.gnupg.agent = {
+    enable = true;
+    enableSSHSupport = true;
+  };
+
+  security.pam.services = {
+    login.u2fAuth = true;
+    sudo.u2fAuth = true;
+  };
+
+  # FIXME Replace [your_yubikey_model_id] with the actual model ID of your YubiKey. You can find the model ID using the `lsusb` command, typically available as a part of the `usbutils` package
+  services.udev.extraRules = ''
+      ACTION=="remove",\
+       ENV{ID_BUS}=="usb",\
+       ENV{ID_MODEL_ID}=="your_yubikey_model_id",\
+       ENV{ID_VENDOR_ID}=="1050",\
+       ENV{ID_VENDOR}=="Yubico",\
+       RUN+="${pkgs.systemd}/bin/loginctl lock-sessions"
+  '';
+
+  environment.systemPackages = with pkgs; [
+    pam_u2f
+  ];
+}