Merge branch 'use-defer-helperfor-ide-xterm' into 'master'

Add helper method for adding page specific styles for IDE-xterm

See merge request gitlab-org/gitlab!44190

ee/app/views/ide/index.html.haml

-- content_for :page_specific_javascripts do
-  = stylesheet_link_tag "xterm.css"
+- add_page_specific_style "xterm.css"
 
 = render partial: "ide/show"