tmux module: do not override keys by default in VI mode (#17330)

We want to stick to upstream defaults as much as possible.

As pointed out by @8573 in #16999, this was not the case.

nixos/modules/programs/tmux.nix

···
     set -g status-keys ${cfg.keyMode}
     set -g mode-keys   ${cfg.keyMode}
 
-    ${if cfg.keyMode == "vi" then ''
+    ${if cfg.keyMode == "vi" && cfg.customPaneNavigationAndResize then ''
     bind h select-pane -L
     bind j select-pane -D
     bind k select-pane -U
···
         example = true;
         type = types.bool;
         description = "Use 24 hour clock.";
+      };
+
+      customPaneNavigationAndResize = mkOption {
+        default = false;
+        example = true;
+        type = types.bool;
+        description = "Override the hjkl and HJKL bindings for pane navigation and resizing in VI mode.";
       };
 
       escapeTime = mkOption {