Added haml-lint and fix warnings (#2773)

* add haml_lint to Gemfile

* add .haml-lint.yml

* fix warnings of haml_lint

app/views/oauth/authorized_applications/index.html.haml

@@ -16,7 +16,7 @@
             = application.name
           - else
             = link_to application.name, application.website, target: '_blank', rel: 'noopener'
-        %th= application.scopes.map { |scope| t(scope, scope: [:doorkeeper, :scopes]) }.join('<br />').html_safe
+        %th!= application.scopes.map { |scope| t(scope, scope: [:doorkeeper, :scopes]) }.join('<br />')
         %td= l application.created_at
         %td
           - unless application.superapp?