[Doc] add missing prop of layout

docs/Layout.md

@@ -51,6 +51,7 @@ const App = () => (
 | `className` | Optional | `string`    | -        | Passed to the root `<div>` component                                  |
 | `error`     | Optional | `Component` | -        | A React component rendered in the content area in case of error       |
 | `menu`      | Optional | `Component` | -        | A React component rendered at the side of the screen                  |
+| `sidebar`   | Optional | `Component` | -        | A React component responsible for rendering the menu (e.g. in a drawer) |
 | `sx`        | Optional | `SxProps`   | -        | Style overrides, powered by MUI System                                |
 
 React-admin injects more props at runtime based on the `<Admin>` props:
@@ -233,6 +234,46 @@ React-admin provides alternative menu layouts that you can use as a base for you
 
 And you can build a totally custom menu using [MUI's `<Menu>` component](https://mui.com/material-ui/react-menu/).
 
+## `sidebar`
+
+You can override the default sidebar using this prop. The default sidebar will display a permanent drawer when the window size is above MUI theme's `sm` breakpoint, and a temporary drawer when the window size is less than that.
+
+If you wish to always display a temporary drawer, you can customize using the following sample code:
+
+```jsx
+// in src/Layout.js
+import * as React from 'react';
+import { Layout } from 'react-admin';
+
+import { MySidebar } from './MySidebar';
+
+export const Layout = (props) => <Layout {...props} sidebar={MySidebar} />;
+
+
+// in src/MySidebar.js
+import * as React from 'react';
+import { Drawer } from '@mui/material';
+import { SidebarClasses, useLocale, useSidebarState } from 'react-admin';
+
+export const MySidebar = ({ children }) => {
+    const [open, setOpen] = useSidebarState();
+    useLocale(); // force redraw on locale change
+
+    const toggleSidebar = () => setOpen(!open);
+
+    return (
+        <Drawer
+            variant="temporary"
+            open={open}
+            onClose={toggleSidebar}
+            classes={SidebarClasses}
+        >
+            {children}
+        </Drawer>
+    );
+};
+```
+
 ## `sx`: CSS API
 
 Pass an `sx` prop to customize the style of the main component and the underlying elements.