feat: finish main layout

src/assets/styles/index.scss

@@ -1,5 +1,5 @@
 html {
-  background-color: #fff;
+  background-color: #fefefe;
 }
 
 body {
@@ -15,53 +15,4 @@ code {
     monospace;
 }
 
-.layout {
-  width: 100%;
-  height: 100%;
-  display: flex;
-
-  &__sidebar {
-    height: 100vh;
-    flex: 1 1 25%;
-    border-right: 1px solid #ccc;
-
-    > h1 {
-      text-align: center;
-      color: #303133;
-    }
-
-    > h3 {
-      text-align: center;
-      color: #909399;
-    }
-  }
-
-  &__links {
-    $link-height: 60px;
-
-    border-top: 1px solid #ccc;
-
-    > a {
-      display: block;
-      width: 100%;
-      height: $link-height;
-      line-height: $link-height;
-      text-align: center;
-      user-select: none;
-      font-size: 24px;
-      color: #606266;
-      border-bottom: 1px solid #ccc;
-      text-decoration: none;
-
-      &.active {
-        background-color: #eee;
-      }
-    }
-  }
-
-  &__content {
-    flex: 1 1 75%;
-    padding: 20px 30px;
-    box-sizing: border-box;
-  }
-}
+@import "./layout.scss";