Define imv keys, switch to btop, put stateful data in per-system config

modules/home/programs/terminal/btop/default.nix

@@ -0,0 +1,11 @@
+{ ... }:
+{
+  programs.btop = {
+    enable = true;
+    settings = {
+      vim_keys = true;
+      rounded_corners = false;
+      theme_background = false;
+    };
+  };
+}

modules/home/programs/terminal/default.nix

@@ -1,6 +1,7 @@
 { ... }:
 {
   imports = [
+    ./btop
     ./fastfetch
     ./git
     ./ncmpcpp