Added tooltip to new issue button

app/views/projects/boards/components/_board.html.haml

@@ -16,10 +16,12 @@
             %span.board-issue-count.pull-left{ ":class" => "{ 'has-btn': list.type !== 'done' }" }
               {{ list.issuesSize }}
             - if can? current_user, :create_issue, @project
-              %button.btn.btn-small.btn-default.pull-right{ type: "button",
+              %button.btn.btn-small.btn-default.pull-right.has-tooltip{ type: "button",
                 "@click" => "showNewIssueForm",
                 "v-if" => "list.type !== 'done'",
-                "aria-label" => "Show new issue form" }
+                "aria-label" => "Add an issue",
+                "title" => "Add an issue",
+                data: { placement: "top", container: "body" } }
                 = icon("plus")
           - if can?(current_user, :admin_list, @project)
             %board-delete{ "inline-template" => true,