[docs] Fix broken link (#11042)

docs/src/pages/customization/default-theme/default-theme.md

@@ -12,5 +12,5 @@ Tip: you can play with the theme object in your console too.
 Please take note that the documentation site is using a custom theme. As a result, the demos
 you see here might disagree with the values above.
 
-If you want to learn more about how the theme is assembled, take a look at [`material-ui/style/createMuiTheme.js`](https://github.com/mui-org/material-ui/blob/v1-beta/src/styles/createMuiTheme.js),
+If you want to learn more about how the theme is assembled, take a look at [`material-ui/style/createMuiTheme.js`](https://github.com/mui-org/material-ui/blob/v1-beta/packages/material-ui/src/styles/createMuiTheme.js),
 and the related imports which `createMuiTheme` uses.

docs/src/pages/customization/overrides/overrides.md

@@ -31,7 +31,7 @@ When the `className` property isn't enough, and you need to access deeper elemen
 The list of  classes for each
 component is documented in the **Component API** section.
 For instance, you can have a look at the [Button CSS API](/api/button#css-api).
-Alternatively, you can always look at the [implementation details](https://github.com/mui-org/material-ui/blob/v1-beta/src/Button/Button.js).
+Alternatively, you can always look at the [implementation details](https://github.com/mui-org/material-ui/blob/v1-beta/packages/material-ui/src/Button/Button.js).
 
 This example also uses `withStyles()` (see above), but here, `OverridesClasses` is using `Button`'s `classes` prop to
 provide an object that maps the **names of classes to override** (keys) to the **CSS class names to apply** (values).

docs/src/pages/customization/themes/themes.md

@@ -301,7 +301,7 @@ That's a really powerful feature.
 
 The list of these customization points for each component is documented under the **Component API** section.
 For instance, you can have a look at the [Button](/api/button#css-api).
-Alternatively, you can always have a look at the [implementation](https://github.com/mui-org/material-ui/blob/v1-beta/src/Button/Button.js).
+Alternatively, you can always have a look at the [implementation](https://github.com/mui-org/material-ui/blob/v1-beta/packages/material-ui/src/Button/Button.js).
 
 ## Accessing the theme in a component
 

docs/src/pages/guides/minimizing-bundle-size/minimizing-bundle-size.md

@@ -32,7 +32,7 @@ import Button from 'material-ui/Button';
 import TextField from 'material-ui/TextField';
 ```
 
-While importing directly in this manner doesn't use the exports in [`material-ui/index.js`](https://github.com/mui-org/material-ui/blob/v1-beta/src/index.js), this file can serve as a handy reference as to which modules are public.
+While importing directly in this manner doesn't use the exports in [`material-ui/index.js`](https://github.com/mui-org/material-ui/blob/v1-beta/packages/material-ui/src/index.js), this file can serve as a handy reference as to which modules are public.
 Anything not listed there should be considered **private**, and subject to change without notice.
 For instance, the `Tabs` component is a public module while `TabIndicator` is private.
 

docs/src/pages/layout/basics/basics.md

@@ -30,7 +30,7 @@ Several Material-UI components utilize `z-index`, the CSS property that helps co
 We utilize a default z-index scale in Material-UI that's been designed to properly layer drawers,
 modals, snackbars, tooltips, and more.
 
-[These values](https://github.com/mui-org/material-ui/blob/v1-beta/src/styles/zIndex.js) start at an arbitrary number, high and specific enough to ideally avoid conflicts.
+[These values](https://github.com/mui-org/material-ui/blob/v1-beta/packages/material-ui/src/styles/zIndex.js) start at an arbitrary number, high and specific enough to ideally avoid conflicts.
 
 - mobile stepper: 1000
 - app bar: 1100