chore: correct hierarchy of BrowserWindow headings

docs/api/browser-window.md

@@ -22,12 +22,13 @@ win.loadFile('index.html')
 To create a window without chrome, or a transparent window in arbitrary shape,
 you can use the [Frameless Window](frameless-window.md) API.
 
-## Showing window gracefully
+## Showing the window gracefully
 
-When loading a page in the window directly, users may see the page load incrementally, which is not a good experience for a native app. To make the window display
-without visual flash, there are two solutions for different situations.
+When loading a page in the window directly, users may see the page load incrementally,
+which is not a good experience for a native app. To make the window display
+without a visual flash, there are two solutions for different situations.
 
-## Using `ready-to-show` event
+### Using the `ready-to-show` event
 
 While loading the page, the `ready-to-show` event will be emitted when the renderer
 process has rendered the page for the first time if the window has not been shown yet. Showing
@@ -48,7 +49,7 @@ event.
 Please note that using this event implies that the renderer will be considered "visible" and
 paint even though `show` is false.  This event will never fire if you use `paintWhenInitiallyHidden: false`
 
-## Setting `backgroundColor`
+### Setting the `backgroundColor` property
 
 For a complex app, the `ready-to-show` event could be emitted too late, making
 the app feel slow. In this case, it is recommended to show the window