feat(tmux): use dracula theme and support plugins

nixos/cfg/packages.nix

@@ -53,6 +53,7 @@
 
   programs = {
 
+    # TODO: install plugins through nix
     tmux = {
       enable = true;
       keyMode = "vi";
@@ -66,6 +67,11 @@
         set -ga terminal-overrides ',xterm*:smcup@:rmcup@'
         bind -T root WheelUpPane   if-shell -F -t = "#{alternate_on}" "send-keys -M" "select-pane -t =; copy-mode -e; send-keys -M"
         bind -T root WheelDownPane if-shell -F -t = "#{alternate_on}" "send-keys -M" "select-pane -t =; send-keys -M"
+
+        set -g @plugin 'dracula/tmux'
+        run 'bash -c "$HOME/.tmux/plugins/tpm/tpm ||
+                      ${pkgs.git}/bin/git clone https://github.com/tmux-plugins/tpm $HOME/.tmux/plugins/tpm &&
+                      $HOME/.tmux/plugins/tpm/tpm"'
       '';
     };