Add styles for light and dark modes

Author: alexdevero

src/assets/css/_example/_example.css

@@ -1,4 +1,19 @@
 /* Example stylesheet */
+@media screen and (prefers-color-scheme: light), screen and (prefers-color-scheme: no-preference) {
+  /*light theme*/
+  body{
+    color: black;
+    background-color: white;
+  }
+}
+
+@media screen and (prefers-color-scheme: dark) {
+  /*dark theme*/
+  body {
+    color: white;
+    background-color: black;
+  }
+}
 
 h1 {
   font-family: helvetica;