feat: replace placeholder core-libraries doc with full core-library reference and refine site design

Replace the empty `core-libraries.markdown` placeholder with a comprehensive `core-library.markdown` documenting Object, Class, Bool, and Fiber classes. Update site template to link to the new page. Tweak SCSS styles: reduce body font to 16px/25px, darken header background with text-shadow, adjust code font size and borders, add left margin to main content paragraphs and pre blocks, and refine link colors. Fix prose in functions.markdown to use "arguments" instead of "parameters" and clarify dynamic dispatch wording.

doc/site/template.html

@@ -48,7 +48,7 @@
     <section>
       <h2>reference</h2>
       <ul>
-        <li><a href="core-libraries.html">Core Libraries</a></li>
+        <li><a href="core-library.html">Core Library</a></li>
         <li><a href="embedding-api.html">Embedding API</a></li>
         <li><a href="performance.html">Performance</a></li>
         <li><a href="contributing.html">Contributing</a></li>
@@ -64,7 +64,7 @@
 <footer>
   <div class="page">
     <div class="main-column">
-    <p>Wren lives <a href="https://github.com/munificent/wren">on GitHub</a> &mdash; Made with &#x2764; by Bob Nystrom.</p>
+    <p>Wren lives <a href="https://github.com/munificent/wren">on GitHub</a> &mdash; Made with &#x2764; by <a href="http://journal.stuffwithstuff.com/">Bob Nystrom</a>.</p>
     <div class="main-column">
   </div>
 </footer>