Add get involved call to action

Signed-off-by: Nico Burns <[email protected]>

Author: nicoburns

_includes/hero.html

@@ -6,6 +6,7 @@ <h1 class="title center-text">
         Servo aims to empower developers with a lightweight, high-performance alternative for embedding web technologies in applications.
       </h1>
       <div class="center-text cta-container">
+        <a class="button button--hero" href="/contributing/">Get Involved</a>
         <a class="button button--hero" target="_blank" href="https://opencollective.com/servo">Donate</a>
       </div>
     </div>

assets/css/style.css.liquid

@@ -439,7 +439,10 @@ nav .inner-container {
 }
 
 .cta-container {
+  display: flex;
+  justify-content: center;
   padding: var(--24px) 0;
+  gap: var(--16px);
 }
 
 .features {