cleanup: trim trailing whitespace (#11136)

* cleanup: trim trailing whitespace

* update(`.editorconfig`)

---------

Co-authored-by: syuilo <Syuilotan@yahoo.co.jp>

packages/frontend/src/directives/adaptive-border.ts

@@ -10,7 +10,7 @@ export default {
 				return el.parentElement ? getBgColor(el.parentElement) : 'transparent';
 			}
 		};
-	
+
 		const parentBg = getBgColor(src.parentElement);
 
 		const myBg = window.getComputedStyle(src).backgroundColor;