highlight.js doesn't like tsx

step2-03/demo/README.md

@@ -21,7 +21,7 @@ There are some predefined themes within Fabric already, like Fluent (which will
 
 The following code (simplified from `demo/src/components/TodoApp.tsx`) shows an example of applying the Fluent theme to our todo app using `Customizer`.
 
-```tsx
+```jsx
 import { Customizer } from 'office-ui-fabric-react';
 import { FluentCustomizations } from '@uifabric/fluent-theme';
 
@@ -128,7 +128,7 @@ Benefits of `mergeStyles` include:
 
 The following is a basic example using mergeStyles. ([This CodePen](https://codepen.io/dzearing/pen/jGdgrE?editors=1011) illustrates in more detail what `mergeStyles` does and includes some advanced examples.)
 
-```tsx
+```jsx
 // can also import from office-ui-fabric-react in Fabric-based apps
 import { mergeStyles } from '@uifabric/merge-styles';
 

step2-03/exercise/README.md

@@ -46,7 +46,7 @@ import { TeamsCustomizations } from '@uifabric/theme-samples';
 
 1. Try generating a class name using `mergeStyles` and use it as a `className` prop inside `TodoApp`
 
-```tsx
+```jsx
 import { mergeStyles } from 'office-ui-fabric-react';
 
 const className = mergeStyles({