docs(readme): syntax-highlight nested snippets in debugging section (#5799)

README.md

@@ -198,22 +198,28 @@ Puppeteer creates its own browser user profile which it **cleans up on every run
    displaying. Instead of launching in headless mode, launch a full version of
    the browser using  `headless: false`:
 
+    ```js
     const browser = await puppeteer.launch({headless: false});
+    ```
 
 2. Slow it down - the `slowMo` option slows down Puppeteer operations by the
    specified amount of milliseconds. It's another way to help see what's going on.
 
+    ```js
     const browser = await puppeteer.launch({
       headless: false,
       slowMo: 250 // slow down by 250ms
     });
+    ```
 
 3. Capture console output - You can listen for the `console` event.
    This is also handy when debugging code in `page.evaluate()`:
 
+    ```js
     page.on('console', msg => console.log('PAGE LOG:', msg.text()));
 
     await page.evaluate(() => console.log(`url is ${location.href}`));
+    ```
 
 4. Use debugger in application code browser
 
@@ -223,7 +229,9 @@ Puppeteer creates its own browser user profile which it **cleans up on every run
 
     - Use `{devtools: true}` when launching Puppeteer:
 
-        `const browser = await puppeteer.launch({devtools: true});`
+      ```js
+      const browser = await puppeteer.launch({devtools: true});
+      ```
 
     - Change default test timeout:
 
@@ -235,7 +243,9 @@ Puppeteer creates its own browser user profile which it **cleans up on every run
 
     - Add an evaluate statement with `debugger` inside / add  `debugger` to an existing evaluate statement:
 
-      `await page.evaluate(() => {debugger;});`
+      ```js
+      await page.evaluate(() => {debugger;});
+      ```
 
        The test will now stop executing in the above evaluate statement, and chromium will stop in debug mode.
 
@@ -248,10 +258,12 @@ Puppeteer creates its own browser user profile which it **cleans up on every run
     you want to try something out, you have to add it to your test file.
 
     - Add `debugger;` to your test, eg:
-      ```
+
+      ```js
       debugger;
       await page.click('a[target=_blank]');
       ```
+
     - Set `headless` to `false`
     - Run `node --inspect-brk`, eg `node --inspect-brk node_modules/.bin/jest tests`
     - In Chrome open `chrome://inspect/#devices` and click `inspect`