Enable resetting the colour scheme to the system appearance

src/_includes/base.njk

@@ -67,6 +67,10 @@
 					<input type="radio" name="color-scheme" value="light">
 					Light
 				</label>
+				<label>
+					<input type="radio" name="color-scheme" value="system">
+					System
+				</label>
 			</fieldset>
 		</header>
 		{{ content | safe }}
@@ -90,11 +94,7 @@
 					return localStorage.getItem('color-scheme');
 				}
 
-				if (window.matchMedia('(prefers-color-scheme: dark)')?.matches) {
-					return "dark";
-				}
-
-				return "light";
+				return "system";
 			};
 
 			const data = new Proxy({
@@ -110,7 +110,7 @@
 			});
 
 			const onRadioChange = e => {
-				data[e.target.name] = e.target.value;
+				data[e.target.name] = e.target.value;					
 			}
 
 			document.querySelectorAll('[name="color-scheme"]').forEach(radio => {