Add report call to action to 404 page

Add call to action.
Small wording changes.
Correct li :last-child margin bottom fault.

404.html

@@ -16,7 +16,9 @@ <h1>Page Not Found</h1>
 <ul>
   <li>Try our search, up in the top right</li>
   <li>Browse through the <a href="/years/">by-year archive</a> of shows and committees</li>
-  <li>Look up <a href="/people/">alumni bios</a></li>
+  <li>Look up <a href="/people/">alumni profiles</a></li>
   <li>Read about the <a href="/history/">history of the Nottingham New Theatre</a></li>
   <li>Start again at the <a href="/">home page.</a></li>
 </ul>
+
+<p>Should there be something here? Let us know by <a href="https://github.com/newtheatre/history-project/issues/new?body={{page.url}}" data-proofer-ignore data-report-this-page>sending the editors a message</a>.</p>

_sass/_type.sass

@@ -236,7 +236,7 @@ ul, ol
   li
     padding-bottom: $baseline
     &:last-child
-      margin-bottom: 0
+      padding-bottom: 0
   &.minimal
     margin-left: 0
   h3, h4, h5, h6