feat(shell): add btop

shell/btop.nix

@@ -0,0 +1,13 @@
+{ ... }:
+
+{
+  programs = {
+    btop = {
+      enable = true;
+      settings = {
+        theme_background = false;
+        vim_keys = true;
+      };
+    };
+  };
+}

shell/default.nix

@@ -12,6 +12,7 @@
   imports = [
     ./atuin.nix
     ./bat.nix
+    ./btop.nix
     ./carapace.nix
     ./direnv.nix
     ./eza.nix