docs: document outlivesOpener option in window open handler (#36507)

* docs: document outlivesOpener option in window open handler

Co-authored-by: Jeremy Rose <jeremya@chromium.org>

* outlivesOpener is optional

Co-authored-by: Jeremy Rose <jeremya@chromium.org>

Co-authored-by: trop[bot] <37223003+trop[bot]@users.noreply.github.com>
Co-authored-by: Jeremy Rose <jeremya@chromium.org>

docs/api/web-contents.md

@@ -1180,7 +1180,7 @@ Ignore application menu shortcuts while this web contents is focused.
 
 #### `contents.setWindowOpenHandler(handler)`
 
-* `handler` Function<{action: 'deny'} | {action: 'allow', overrideBrowserWindowOptions?: BrowserWindowConstructorOptions}>
+* `handler` Function<{action: 'deny'} | {action: 'allow', outlivesOpener?: boolean, overrideBrowserWindowOptions?: BrowserWindowConstructorOptions}>
   * `details` Object
     * `url` string - The _resolved_ version of the URL passed to `window.open()`. e.g. opening a window with `window.open('foo')` will yield something like `https://the-origin/the/current/path/foo`.
     * `frameName` string - Name of the window provided in `window.open()`
@@ -1195,8 +1195,11 @@ Ignore application menu shortcuts while this web contents is focused.
       be set. If no post data is to be sent, the value will be `null`. Only defined
       when the window is being created by a form that set `target=_blank`.
 
-  Returns `{action: 'deny'} | {action: 'allow', overrideBrowserWindowOptions?: BrowserWindowConstructorOptions}` - `deny` cancels the creation of the new
+  Returns `{action: 'deny'} | {action: 'allow', outlivesOpener?: boolean, overrideBrowserWindowOptions?: BrowserWindowConstructorOptions}` - `deny` cancels the creation of the new
   window. `allow` will allow the new window to be created. Specifying `overrideBrowserWindowOptions` allows customization of the created window.
+  By default, child windows are closed when their opener is closed. This can be
+  changed by specifying `outlivesOpener: true`, in which case the opened window
+  will not be closed when its opener is closed.
   Returning an unrecognized value such as a null, undefined, or an object
   without a recognized 'action' value will result in a console error and have
   the same effect as returning `{action: 'deny'}`.