ammending copyright to reference Swift project authors as well

Author: heckj

common/footer.html

@@ -14,7 +14,7 @@
 </style>
 
 <footer id="footer" class="minimal-footer">
-  <p>Copyright &copy; {{COPYRIGHT_YEAR}} Apple Inc. All rights reserved.</p>
+  <p>Copyright &copy; {{COPYRIGHT_YEAR}} Apple Inc. and the Swift project authors. All rights reserved.</p>
   <p>Swift and the Swift logo are trademarks of Apple Inc.</p>
   <nav aria-label="Legal">
     <ul>