feat: add Cmd+, keyboard shortcut to toggle settings (#319)

Add settings.toggle action with Cmd+, (Mac) / Ctrl+, (non-Mac) bindings.
When on a settings route, pressing the shortcut navigates back; otherwise
it pushes to the host settings route. Also adds comma to the shortcut
key map so the combo string parses correctly.

packages/app/src/keyboard/actions.ts

@@ -37,6 +37,7 @@ export type KeyboardActionId =
   | "sidebar.toggle.left"
   | "sidebar.toggle.right"
   | "sidebar.toggle.both"
+  | "settings.toggle"
   | "command-center.toggle"
   | "shortcuts.dialog.toggle"
   | "workspace.terminal.new"