refactored nixos directory & updated README

nixos/linux-kernel.nix

@@ -0,0 +1,34 @@
+{ pkgs, ... }:
+
+{
+  # Linux Kernel
+  boot.kernelPackages = pkgs.linuxKernel.packages.linux_lqx;
+  boot.kernelParams = [ 
+    "quiet"
+    "fbcon=nodefer"
+    "vt.global_cursor_default=0"
+    "kernel.modules_disabled=1"
+    "lsm=landlock,lockdown,yama,integrity,apparmor,bpf,tomoyo,selinux"
+    "usbcore.autosuspend=-1"
+    "video4linux"
+    "acpi_rev_override=5"
+    "security=selinux"
+  ];
+  # boot.kernelPatches = [ {
+  #      name = "selinux-config";
+  #      patch = null;
+  #      extraConfig = '' 
+  #              SECURITY_SELINUX y
+  #              SECURITY_SELINUX_BOOTPARAM n
+  #              SECURITY_SELINUX_DEVELOP y
+  #              SECURITY_SELINUX_AVC_STATS y
+  #              DEFAULT_SECURITY_SELINUX n
+  #            '';
+  # } ];
+
+  systemd.package = pkgs.systemd.override { withSelinux = true; };
+
+  environment.systemPackages = with pkgs; [
+    policycoreutils
+  ];
+}