Make "try it online" bigger.

index.html

@@ -83,8 +83,9 @@ layout: default
     <h2>Get diffoscope</h2>
     <ul>
       <li>
-        <a href="https://try.diffoscope.org/">Try it online!</a>
+        <strong><a href="https://try.diffoscope.org/">Try it online!</a></strong>
       </li>
+
       <li>
         Via <a href="https://pypi.python.org/"><code>pip</code></a>:<br />
         <code>pip install diffoscope</code><br />