Add show code

docs/_sass/example.sass

@@ -42,6 +42,10 @@
     margin-top: -1.5rem
     &:not(:last-child)
       margin-bottom: 1.5rem
+  & + .bd-highlight-clipped
+    margin-top: -1.5rem
+    &:not(:last-child)
+      margin-bottom: 1.5rem
 
 // Snippet
 .bd-snippet
@@ -210,6 +214,33 @@ $structure-invert: $danger-invert
     pre
       white-space: pre-wrap
 
+.bd-highlight-clipped
+  .bd-show
+    +overlay
+    align-items: center
+    background-color: rgba(#000, 0.9)
+    background-image: linear-gradient(rgba(#000, 0), rgba(#000, 0) 90%, rgba(#000, 1))
+    border: none
+    color: $white
+    cursor: pointer
+    display: none
+    font-size: $size-6
+    justify-content: center
+    opacity: 0.7
+    width: 100%
+    strong
+      color: currentColor
+      font-weight: $weight-semibold
+    &:hover
+      opacity: 0.8
+  .highlight.bd-is-clipped
+    height: 4em
+    overflow: hidden
+    pre
+        overflow: hidden
+    .bd-show
+      display: flex
+
 +tablet
   .section:not(.is-fullwidth) > .bd-example:not(.is-fullwidth)
     margin-left: 1.5rem