[readme] changed frametime_alpha to alpha

README.md

@@ -71,7 +71,8 @@ A partial list of parameters are below. See the config file for a complete list.
 | `toggle_hud=`<br>`toggle_logging=` | Modifiable toggle hotkeys. Default are F12 and F2, respectively.                      |
 | `time`<br>`time_format=%T`         | Displays local time. See [std::put_time](https://en.cppreference.com/w/cpp/io/manip/put_time) for formatting help. |
 | `gpu_color`<br>`gpu_color`<br>`vram_color`<br>`ram_color`<br>`io_color`<br>`engine_color`<br>`frametime_color`<br>`background_color`         | Change default colors: `gpu_color=RRGGBB`|
-| `background_alpha`<br>`frametime_alpha`| Set the opacity of the background and frametime line `0.0-1.0`|
+| `alpha`                            | Set the opacity of all text and frametime graph `0.0-1.0`                             |
+| `background_alpha`                 | Set the opacity of the background `0.0-1.0`                                           |
 
 Note: Width and Height are set automatically based on the font_size, but can be overridden.