Add docs for the styles.widgets.bg_color option

Author: dastarruer

docs/content/configuration/config-file/styling.md

@@ -162,6 +162,7 @@ These can be set under `[styles.widgets]`:
 | `border_color`          | The colour of the widgets' borders                                                           | `border_color = "white"`                                              |
 | `selected_border_color` | The colour of a widget's borders when the widget is selected                                 | `selected_border_color = "white"`                                     |
 | `widget_title`          | Text styling for a widget's title                                                            | `widget_title = { color = "black", bg_color = "blue", bold = true }`  |
+| `bg_color`          | The background color of the widgets.                                                            | `bg_color = "black"`  |
 | `text`                  | Text styling for text in general                                                             | `text = { color = "black", bg_color = "blue", bold = true }`          |
 | `selected_text`         | Text styling for text when representing something that is selected                           | `selected_text = { color = "black", bg_color = "blue", bold = true }` |
 | `disabled_text`         | Text styling for text when representing something that is disabled                           | `disabled_text = { color = "black", bg_color = "blue", bold = true }` |