style: 按钮居中

src/layouts/index.scss

@@ -6,6 +6,8 @@
   box-sizing: border-box;
   height: 55px;
   background: linear-gradient(135deg, var(--ev-c-primary), var(--ev-c-dark));
+  display: flex;
+  align-items: center;
 }
 .el-main {
   box-sizing: border-box;