[Doc]: Fix links

docs/Admin.md

@@ -278,7 +278,7 @@ For more details on predefined themes and custom themes, refer to the [Material
 
 If you want to deeply customize the app header, the menu, or the notifications, the best way is to provide a custom layout component. It must contain a `{children}` placeholder, where react-admin will render the resources. If you use material UI fields and inputs, it should contain a `<ThemeProvider>` element. And finally, if you want to show the spinner in the app header when the app fetches data in the background, the Layout should connect to the redux store.
 
-Use the [default layout](https://github.com/marmelab/react-admin/blob/master/packages/ra-ui-materialui/src/layout/Layout.js) as a starting point, and check [the Theming documentation](./Theming.md#using-a-custom-layout) for examples.
+Use the [default layout](https://github.com/marmelab/react-admin/blob/master/packages/ra-ui-materialui/src/layout/Layout.tsx) as a starting point, and check [the Theming documentation](./Theming.md#using-a-custom-layout) for examples.
 
 ```jsx
 // in src/App.js

docs/Theming.md

@@ -514,7 +514,7 @@ const MyLayout = props => <Layout {...props} sidebar={MySidebar} />
 
 ### Layout From Scratch
 
-For more custom layouts, write a component from scratch. It must contain a `{children}` placeholder, where react-admin will render the resources. Use the [default layout](https://github.com/marmelab/react-admin/blob/master/packages/ra-ui-materialui/src/layout/Layout.js) as a starting point. Here is a simplified version (with no responsive support):
+For more custom layouts, write a component from scratch. It must contain a `{children}` placeholder, where react-admin will render the resources. Use the [default layout](https://github.com/marmelab/react-admin/blob/master/packages/ra-ui-materialui/src/layout/Layout.tsx) as a starting point. Here is a simplified version (with no responsive support):
 
 ```jsx
 // in src/MyLayout.js

docs/UnitTesting.md

@@ -93,7 +93,7 @@ As explained on the [Authorization page](./Authorization.md), it's possible to m
 
 In order to avoid regressions and make the design explicit to your co-workers, it's better to unit test which fields is supposed to be displayed or hidden for each permission.
 
-Here is an example with Jest and Enzyme, which is testing the [User `show` page of the simple example](https://github.com/marmelab/react-admin/blob/master/examples/simple/src/users/UserShow.js).
+Here is an example with Jest and Enzyme, which is testing the [`UserShow` page of the simple example](https://github.com/marmelab/react-admin/blob/master/examples/simple/src/users/UserShow.js).
 
 ```jsx
 // UserShow.spec.js

packages/ra-i18n-polyglot/README.md

@@ -60,7 +60,7 @@ The `message` returned by the function argument should be a dictionary where the
 
 All core translations are in the `ra` namespace, in order to prevent collisions with your own custom translations. The root key used at runtime is determined by the value of the `locale` prop.
 
-The default messages are available [here](https://github.com/marmelab/react-admin/blob/master/packages/ra-language-english/index.js).
+The default messages are available [here](https://github.com/marmelab/react-admin/blob/master/packages/ra-language-english/src/index.ts).
 
 ## Asynchronous Locale Change