Add codepen icon

CHANGELOG.md

@@ -21,6 +21,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
   - `chevrons-right`
   - `chevrons-up`
   - `cloud-snow`
+  - `codepen`
   - `repeat`
 </details>
 

icons/logos/codepen.svg

+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24">
+    <polygon points="12 2 22 8.5 22 15.5 12 22 2 15.5 2 8.5 12 2" fill="none" stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="2"/>
+    <line x1="12" y1="22" x2="12" y2="15.5" fill="none" stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="2"/>
+    <polyline points="22 8.5 12 15.5 2 8.5" fill="none" stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="2"/>
+    <polyline points="2 15.5 12 8.5 22 15.5" fill="none" stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="2"/>
+    <line x1="12" y1="2" x2="12" y2="8.5" fill="none" stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="2"/>
+</svg>