Add syntax highlighting

contributing.md

@@ -23,7 +23,7 @@ To get started simply:
 
 The src/main.test.ts file contains integration tests that validate all the features of this action, to add a new test case simply add a new function to the bottom of this file.
 
-```
+```typescript
 test('Name of test goes here', async () => {
     // This method creates a test repository in your temp directory, the repo
     // object returned provides methods to interact with the repository

readme.md

@@ -167,7 +167,7 @@ This history is required to determine the version correctly. To include the hist
 and tags, specify the fetch-depth parameter in your checkout action declaration. Specify
 zero to pull the full history and tags.
 
-```
+```yaml
   - name: Checkout
     uses: actions/checkout@v2
     with: