style: Refine header font and checkbox styles

mapper/src/App.css

@@ -104,6 +104,7 @@ h2 {
 	font-size: 1.5rem;
 	color: white;
 	cursor: pointer;
+	font-family: sans-serif;
 
 	/* Center content */
 	display: flex;
@@ -127,8 +128,8 @@ h2 {
 	/* Custom checkbox style */
 	font: inherit;
 	color: currentColor;
-	width: 1.15em;
-	height: 1.15em;
+	width: 0.75em;
+	height: 0.75em;
 	border: 0.1em solid currentColor;
 	border-radius: 0;
 	transform: translateY(-0.075em);