chore: remove custom scroll bar

Non-standard: This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

https://developer.mozilla.org/en-US/docs/Web/CSS/::-webkit-scrollbar

The system default overlay scroll bar is actually better.

assets/css/_core/_base.scss

@@ -15,22 +15,6 @@ html {
 	}
 }
 
-/* scrollbar, only support webkit */
-@if $custom-scrollbar {
-  ::-webkit-scrollbar {
-    width: .5rem;
-    height: .5rem;
-  }
-
-  ::-webkit-scrollbar-thumb {
-    background-color: $custom-scrollbar-color;
-
-    &:hover {
-      background-color: $custom-scrollbar-hover-color;
-    }
-  }
-}
-
 ::selection {
   background-color: $selection-color;
 }

assets/css/_page/_single.scss

@@ -153,16 +153,6 @@
     .table-wrapper {
       overflow-x: auto;
 
-      @if $custom-scrollbar {
-        &::-webkit-scrollbar {
-          background-color: $table-background-color;
-        }
-
-        ::-webkit-scrollbar-corner {
-          background-color: $table-background-color;
-        }
-      }
-
       >table {
         width: 100%;
         max-width: 100%;

assets/css/_variables.scss

@@ -28,17 +28,6 @@ $global-link-hover-color: var(--global-link-hover-color) !default;
 $global-border-color: var(--global-border-color) !default;
 // ========== Global ========== //
 
-// ========== Scrollbar ========== //
-// Whether enable custom scrollbar
-$custom-scrollbar: true;
-$custom-scrollbar-width: .5rem;
-$custom-scrollbar-height: .5rem;
-// Color of the scrollbar
-$custom-scrollbar-color: #87878d !default;
-// Color of the hover scrollbar
-$custom-scrollbar-hover-color: #a9a9b3 !default;
-// ========== Scrollbar ========== //
-
 // ========== Selection ========== //
 // Color of the selected text
 $selection-color: var(--selection-color) !default;