Add sticky sidebar on wiki page

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

-%aside.right-sidebar.right-sidebar-expanded.wiki-sidebar.js-wiki-sidebar
+%aside.right-sidebar.right-sidebar-expanded.wiki-sidebar.js-wiki-sidebar{ data: { "offset-top" => "101", "spy" => "affix" } }
   .block.wiki-sidebar-header.append-bottom-default
     %a.gutter-toggle.pull-right.visible-xs-block.visible-sm-block.js-sidebar-wiki-toggle{ href: "#" }
       = icon('angle-double-right')

app/views/shared/issuable/_sidebar.html.haml

@@ -2,7 +2,7 @@
 - content_for :page_specific_javascripts do
   = page_specific_javascript_bundle_tag('issuable')
-%aside.right-sidebar{ class: sidebar_gutter_collapsed_class, 'aria-live' => 'polite' }
+%aside.right-sidebar{ data: { "offset-top" => "101", "spy" => "affix" }, class: sidebar_gutter_collapsed_class, 'aria-live' => 'polite' }
   .issuable-sidebar
     - can_edit_issuable = can?(current_user, :"admin_#{issuable.to_ability_name}", @project)
     .block.issuable-sidebar-header