Update actions/checkout action to v4

src/scss/main.scss

@@ -24,6 +24,14 @@ body {
   margin: 0;
 }
 
+a {
+  color: #444;
+
+  &:hover {
+    color: #222;
+  }
+}
+
 header {
   position: relative;
   height: 100%;
@@ -286,7 +294,7 @@ section {
           display: block;
           font-size: 20px;
           font-weight: bold;
-          color: $primary;
+          color: #666;
         }
       }