Fix docs for default statusline config (#7720)

book/src/configuration.md

@@ -89,9 +89,9 @@ The `[editor.statusline]` key takes the following sub-keys:
 
 | Key           | Description | Default |
 | ---           | ---         | ---     |
-| `left`        | A list of elements aligned to the left of the statusline | `["mode", "spinner", "file-name"]` |
+| `left`        | A list of elements aligned to the left of the statusline | `["mode", "spinner", "file-name", "file-modification-indicator"]` |
 | `center`      | A list of elements aligned to the middle of the statusline | `[]` |
-| `right`       | A list of elements aligned to the right of the statusline | `["diagnostics", "selections", "position", "file-encoding"]` |
+| `right`       | A list of elements aligned to the right of the statusline | `["diagnostics", "selections", "register", "position", "file-encoding"]` |
 | `separator`   | The character used to separate elements in the statusline | `"│"` |
 | `mode.normal` | The text shown in the `mode` element for normal mode | `"NOR"` |
 | `mode.insert` | The text shown in the `mode` element for insert mode | `"INS"` |