Added collapsible element

_entries/01 introduction.md

@@ -14,4 +14,13 @@ The format of this workshop is a bit different. You'll notice that you won't fin
 
 We kindly ask you not to share this content outside of the challenge so as not to give it away for future participants :)
 
-Enjoy and have fun!
+Enjoy and have fun!
+
+{% collapsible %}
+This is hidden
+
+```
+This is hidden code
+```
+
+{% endcollapsible %}

_plugins/collapsible_tag.rb

@@ -0,0 +1,15 @@
+module Jekyll
+  class CollapsibleTagBlock < Liquid::Block
+
+    def render(context)
+      text = super
+      "<button class=\"collapsible\">Show solution</button>"
+      "<div class=\"collapsible-content\">""
+        #{text}
+      </div>"
+    end
+
+  end
+end
+
+Liquid::Template.register_tag('collapsible', Jekyll::CollapsibleTagBlock)

_sass/partials/_general.scss

@@ -238,4 +238,27 @@ p + p{
 }
 .content li{
   
+}
+
+button.collapsible {
+  background-color: #777;
+  color: white;
+  cursor: pointer;
+  padding: 18px;
+  width: 100%;
+  border: none;
+  text-align: left;
+  outline: none;
+  font-size: 15px;
+}
+
+button.active, button.collapsible:hover {
+  background-color: #555;
+}
+
+.collapsible-content {
+  padding: 0 18px;
+  display: none;
+  overflow: hidden;
+  background-color: #f1f1f1;
 }