docs: show the code of adding devtools extension (electron#16186)

moshfeu · Cheng Zhao · commit 05755ba202e9 · 2019-01-15T17:48:21.000+09:00
diff --git a/docs/tutorial/devtools-extension.md b/docs/tutorial/devtools-extension.md
@@ -29,7 +29,14 @@ Using the [React Developer Tools][react-devtools] as example:
    * on macOS it is `~/Library/Application Support/Google/Chrome/Default/Extensions`.
 1. Pass the location of the extension to `BrowserWindow.addDevToolsExtension`
    API, for the React Developer Tools, it is something like:
-   `~/Library/Application Support/Google/Chrome/Default/Extensions/fmkadmapgofadopljbjfkapdkoienihi/0.15.0_0`
+   ```javascript
+   const path = require('path')
+   const os = require('os')
+
+   BrowserWindow.addDevToolsExtension(
+      path.join(os.homedir(), '/Library/Application Support/Google/Chrome/Default/Extensions/fmkadmapgofadopljbjfkapdkoienihi/0.15.0_0')
+   )
+   ```
 
 **Note:** The `BrowserWindow.addDevToolsExtension` API cannot be called before the
 ready event of the app module is emitted.
