Add "New Page" button to Wiki Pages tab

Closes #2998

CHANGELOG

@@ -45,6 +45,7 @@ v 8.1.0 (unreleased)
   - Fix position of hamburger in header for smaller screens (Han Loong Liauw)
   - Fix bug where Emojis in Markdown would truncate remaining text (Sakata Sinji)
   - Persist filters when sorting on admin user page (Jerry Lukins)
+  - Add "New Page" button to Wiki Pages tab (Stan Hu)
 v 8.0.4
   - Fix Message-ID header to be RFC 2111-compliant to prevent e-mails being dropped (Stan Hu)

app/views/projects/wikis/pages.html.haml

@@ -3,6 +3,7 @@
 = render 'nav'
 .gray-content-block
+  = render 'main_links'
   %h3.page-title
     All Pages
 %ul.content-list