feat(code): add support for code block folding (#259)

assets/css/_partial/_single/_admonition.scss

@@ -9,23 +9,32 @@
   .admonition-title {
     margin: 0 -0.75rem;
     padding: .2rem .75rem .2rem 1.8rem;
-    border-bottom: .05rem solid map-get($admonition-background-color-map, 'note');
+    border-bottom: 1px solid map-get($admonition-background-color-map, 'note');
     background-color: map-get($admonition-background-color-map, 'note');
   }
 
+  .details-summary.admonition-title:hover {
+    background-color: darken(map-get($admonition-background-color-map, 'note'), 6%);
+  }
+
   .admonition-content {
-    margin: .5rem 0;
+    padding: .5rem 0;
   }
 
   i.icon {
     font-size: 0.85rem;
     color: map-get($admonition-color-map, 'note');
-    cursor: auto;
     position: absolute;
     left: .6rem;
     top: .6rem;
   }
 
+  i.details-icon {
+    position: absolute;
+    top: .5rem;
+    right: .5rem;
+  }
+
   @each $type, $color in $admonition-color-map {
     &.#{$type} {
       border-left-color: $color;
@@ -44,6 +53,10 @@
         border-bottom-color: $color;
         background-color: $color;
       }
+
+      .details-summary.admonition-title:hover {
+        background-color: darken($color, 6%);
+      }
     }
   }
 
@@ -51,32 +64,3 @@
     margin-bottom: .75rem;
   }
 }
-
-details.admonition {
-  summary {
-    display: block;
-    outline: none;
-    cursor: pointer;
-
-    &::-webkit-details-marker {
-      display: none;
-    }
-
-    i.details {
-      position: absolute;
-      top: .5rem;
-      right: .5rem;
-      color: $global-font-color;
-
-      .dark & {
-        color: $global-font-color-dark;
-      }
-    }
-  }
-}
-
-details.admonition[open] {
-  i.details {
-    @include transform(rotate(180deg));
-  }
-}