Update custom.css

Author: sheenhx

src/css/custom.css

@@ -28,3 +28,19 @@
   --ifm-color-primary-lightest: #4fddbf;
   --docusaurus-highlighted-code-line-bg: rgba(0, 0, 0, 0.3);
 }
+
+.big-button {
+    display: inline-block;
+    padding: 10px 20px;
+    margin: 5px;
+    background-color: #0070f3;
+    color: white;
+    text-decoration: none;
+    font-size: 18px;
+    border-radius: 5px;
+    transition: background-color 0.3s;
+}
+
+.big-button:hover {
+    background-color: #0056b3;
+}