settings_panel: Bind vim keys to SettingsPanelMenu.

Added a commit to bind vim keys with the SettingsPanelMenu,
allowing users to control the settings and organization tabs
using 'h','j','k' and 'l' keys.

vim_left('h') -> Switch between tab by shifting focus to the left.
vim_right('l') -> Switch between tab by shifting focus to the right.
vim_up('k') -> Move up.
vim_down('j') -> Move down.

static/js/keydown_util.js

@@ -8,6 +8,10 @@ const keys = {
     38: "up_arrow",
     39: "right_arrow",
     40: "down_arrow",
+    72: "vim_left",
+    74: "vim_down",
+    75: "vim_up",
+    76: "vim_right",
 };
 
 export function handle(opts) {

static/js/settings_panel_menu.js

@@ -70,6 +70,12 @@ export class SettingsPanelMenu {
                 enter_key: () => this.enter_panel(),
                 up_arrow: () => this.prev(),
                 down_arrow: () => this.next(),
+
+                // Binding vim keys as well
+                vim_left: toggler.maybe_go_left,
+                vim_right: toggler.maybe_go_right,
+                vim_up: () => this.prev(),
+                vim_down: () => this.next(),
             },
         });
     }