B2B-88: add starter kit structure and elements

packages/ui/src/makerkit/context/sidebar.context.ts

@@ -0,0 +1,11 @@
+import { createContext } from 'react';
+
+const SidebarContext = createContext<{
+  collapsed: boolean;
+  setCollapsed: (collapsed: boolean) => void;
+}>({
+  collapsed: false,
+  setCollapsed: (_) => _,
+});
+
+export { SidebarContext };