:memo: Update docs styles

* Adjust line length to `80`
* Change platform marker `*` to `_`
* Enhance a note section

[ci skip]

docs/api/power-monitor.md

@@ -26,10 +26,10 @@ Emitted when the system is suspending.
 
 Emitted when system is resuming.
 
-### Event: 'on-ac' *Windows*
+### Event: 'on-ac' _Windows_
 
 Emitted when the system changes to AC power.
 
-### Event: 'on-battery' *Windows*
+### Event: 'on-battery' _Windows_
 
 Emitted when system changes to battery power.

docs/faq/electron-faq.md

@@ -145,7 +145,9 @@ is very likely you are using the module in the wrong process. For example
 is only available in renderer processes.
 
 ## Why is my app's background transparent?
-Since Electron `0.37.3`, the default user-agent background color is `transparent`. Simply specify a background color in HTML;
+
+Since Electron `0.37.3`, the default user-agent background color is `transparent`.
+Simply specify a background color in HTML:
 
 ```html
 <style type='text/css'>

docs/tutorial/desktop-environment-integration.md

@@ -15,7 +15,7 @@ to the user. Electron conveniently allows developers to send notifications with
 the [HTML5 Notification API](https://notifications.spec.whatwg.org/), using
 the currently running operating system's native notification APIs to display it.
 
-Note: since this is an HTML5 API it is only available in the renderer process.
+__Note:__ Since this is an HTML5 API it is only available in the renderer process.
 
 ```javascript
 var myNotification = new Notification('Title', {