Update actions/checkout action to v4

src/scss/main.scss

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