Update style.css

Author: Key-code-ai

style.css

@@ -30,6 +30,13 @@ h1, h2, h3 {
   border-bottom: dashed 0.1em var(--theme-color);
 }
 
+header {
+  height: 300px;
+  background-image: url("images/header.jpg");
+  background-size: cover;
+  background-position: center;
+}
+
 /* --------------------
         リンク
 -------------------- */