add(apps): bottom

Added `btm`; a lightweight, diagnostic application. It is preferrable to
`btop`.

apps/bottom/default.nix

@@ -0,0 +1,7 @@
+{pkgs}: {
+  programs.bottom = {
+    enable = true;
+    settings = {
+    };
+  };
+}

modules/home/apps.nix

@@ -6,6 +6,7 @@
     ../../apps/zathura
     ../../apps/mpv
     ../../apps/mako
+    ../../apps/bottom
     # ../../apps/starship
   ];
 }