docs(contributing): re-add qwik-ui codecave image

Author: maiieul

apps/website/src/routes/(main)/contributing/index.mdx

@@ -10,6 +10,10 @@ import { statusByComponent } from '~/_state/component-statuses';
 
 Thinking about contributing to the project, but don't know where to start? You're in the right place!
 
+We'll get you up in shape in no time, and ready to hop into the Qwik UI code cave.
+
+![The Qwik UI Code Cave](/images/contributing/code-cave.webp)
+
 ## There are **two projects** we currently work on:
 
 ### Qwik UI Headless