docs: updated webview tag docs to reflect preload behavior with .asar

docs/api/webview-tag.md

@@ -142,12 +142,16 @@ browser plugins. Plugins are disabled by default.
 ### `preload`
 
 ```html
+<!-- from a file -->
 <webview src="https://www.github.com/" preload="./test.js"></webview>
+<!-- or if you want to load from an asar archive -->
+<webview src="https://www.github.com/" preload="./app.asar/test.js"></webview>
 ```
 
 A `String` that specifies a script that will be loaded before other scripts run in the guest
-page. The protocol of script's URL must be either `file:` or `asar:`, because it
-will be loaded by `require` in guest page under the hood.
+page. The protocol of script's URL must be `file:` (even when using `asar:` archives) because
+it will be loaded by Node's `require` under the hood, which treats `asar:` archives as virtual
+directories.
 
 When the guest page doesn't have node integration this script will still have
 access to all Node APIs, but global objects injected by Node will be deleted