add backToTop button

src/assets/global.css

@@ -123,3 +123,33 @@
     display: block;
   }
 }
+
+#back-to-top {
+  position: fixed;
+  bottom: 20px;
+  right: 20px;
+  background-color: #dfd3c3;
+  color: #333;
+  width: 50px;
+  height: 50px;
+  border-radius: 50%;
+  border: none;
+  cursor: pointer;
+  display: none; /* 初始状态隐藏 */
+  align-items: center;
+  justify-content: center;
+  font-size: 24px;
+  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
+  z-index: 1000;
+  transition: all 0.3s ease; /* 添加过渡效果 */
+}
+
+#back-to-top:hover {
+  background-color: #d0c3b4; /* 稍微深一点的颜色作为悬停效果 */
+  transform: translateY(-3px); /* 悬停时稍微上移 */
+}
+
+#back-to-top:active {
+  transform: translateY(1px); /* 点击时下移，创造按压效果 */
+  box-shadow: 0 1px 5px rgba(0, 0, 0, 0.2); /* 减小阴影 */
+}