docs: added info on bookmark return values for securityScopedBookmarks (#21873)

docs/api/dialog.md

@@ -118,7 +118,7 @@ Returns `Promise<Object>` - Resolve with an object containing the following:
 
 * `canceled` Boolean - whether or not the dialog was canceled.
 * `filePaths` String[] - An array of file paths chosen by the user. If the dialog is cancelled this will be an empty array.
-* `bookmarks` String[] (optional) _macOS_ _mas_ - An array matching the `filePaths` array of base64 encoded strings which contains security scoped bookmark data. `securityScopedBookmarks` must be enabled for this to be populated.
+* `bookmarks` String[] (optional) _macOS_ _mas_ - An array matching the `filePaths` array of base64 encoded strings which contains security scoped bookmark data. `securityScopedBookmarks` must be enabled for this to be populated. (For return values, see [table here](#bookmarks-array).)
 
 The `browserWindow` argument allows the dialog to attach itself to a parent window, making it modal.
 
@@ -200,7 +200,7 @@ The `filters` specifies an array of file types that can be displayed, see
 Returns `Promise<Object>` - Resolve with an object containing the following:
   * `canceled` Boolean - whether or not the dialog was canceled.
   * `filePath` String (optional) - If the dialog is canceled, this will be `undefined`.
-  * `bookmark` String (optional) _macOS_ _mas_ - Base64 encoded string which contains the security scoped bookmark data for the saved file. `securityScopedBookmarks` must be enabled for this to be present.
+  * `bookmark` String (optional) _macOS_ _mas_ - Base64 encoded string which contains the security scoped bookmark data for the saved file. `securityScopedBookmarks` must be enabled for this to be present. (For return values, see [table here](#bookmarks-array).)
 
 The `browserWindow` argument allows the dialog to attach itself to a parent window, making it modal.
 
@@ -335,6 +335,17 @@ On Windows the options are more limited, due to the Win32 APIs used:
 * The `browserWindow` argument is ignored since it is not possible to make
    this confirmation dialog modal.
 
+## Bookmarks array
+
+`showOpenDialog`, `showOpenDialogSync`, `showSaveDialog`, and `showSaveDialogSync` will return a `bookmarks` array.
+
+| Build Type | securityScopedBookmarks boolean | Return Type | Return Value                   |
+|------------|---------------------------------|:-----------:|--------------------------------|
+| macOS mas  | True                            |   Success   | `['LONGBOOKMARKSTRING']`       |
+| macOS mas  | True                            |    Error    | `['']` (array of empty string) |
+| macOS mas  | False                           |      NA     | `[]` (empty array)             |
+| non mas    | any                             |      NA     | `[]` (empty array)             |
+
 ## Sheets
 
 On macOS, dialogs are presented as sheets attached to a window if you provide