feat(compatibility): improve compatibility for Hugo basic version (#352)

assets/css/_partial/_header.scss

@@ -142,10 +142,14 @@ header {
 
 #header-desktop {
   display: block;
-  position: $header-position-desktop;
+  position: fixed;
   height: $header-height;
   line-height: $header-height;
 
+  [header-desktop=normal] & {
+    position: static;
+  }
+
   .header-wrapper {
     padding: 0 2rem 0 10vh;
 
@@ -203,10 +207,14 @@ header {
 
 #header-mobile {
   display: none;
-  position: $header-position-mobile;
+  position: fixed;
   height: $header-height;
   line-height: $header-height;
 
+  [header-mobile=normal] & {
+    position: static;
+  }
+
   .header-container {
     padding: 0;
     margin: 0;

assets/css/_partial/_single/_toc.scss

@@ -55,10 +55,14 @@
   border-left: 4px solid $global-border-color;
   @include overflow-wrap(break-word);
   box-sizing: border-box;
-  top: if($header-normal-mode-desktop, 5rem, 10rem);
+  top: 10rem;
   left: 0;
   visibility: hidden;
 
+  [header-desktop=normal] & {
+    top: 5rem;
+  }
+
   @include blur;
 
   [theme=dark] & {