Added haml-lint and fix warnings (#2773)

* add haml_lint to Gemfile

* add .haml-lint.yml

* fix warnings of haml_lint

app/views/about/_contact.html.haml

@@ -7,7 +7,7 @@
         .name
           = link_to TagManager.instance.url_for(contact.contact_account) do
             %span.display_name.emojify= display_name(contact.contact_account)
-            %span.username= "@#{contact.contact_account.acct}"
+            %span.username @#{contact.contact_account.acct}
 
     - if contact.site_contact_email
       .contact-email

app/views/about/_registration.html.haml

@@ -11,12 +11,12 @@
     required: true,
     input_html: { 'aria-label' => t('simple_form.labels.defaults.email') }
   = f.input :password,
-    autocomplete: "off",
+    autocomplete: 'off',
     placeholder: t('simple_form.labels.defaults.password'),
     required: true,
     input_html: { 'aria-label' => t('simple_form.labels.defaults.password') }
   = f.input :password_confirmation,
-    autocomplete: "off",
+    autocomplete: 'off',
     placeholder: t('simple_form.labels.defaults.confirm_password'),
     required: true,
     input_html: { 'aria-label' => t('simple_form.labels.defaults.confirm_password') }

app/views/about/more.html.haml

@@ -8,7 +8,7 @@
         %h2= site_hostname
 
         - unless @instance_presenter.site_description.blank?
-          %p= @instance_presenter.site_description.html_safe
+          %p!= @instance_presenter.site_description
 
       .information-board
         .section
@@ -25,7 +25,7 @@
           %span= t 'about.domain_count_after'
 
       - unless @instance_presenter.site_extended_description.blank?
-        .panel= @instance_presenter.site_extended_description.html_safe
+        .panel!= @instance_presenter.site_extended_description
 
     .sidebar
       = render 'contact', contact: @instance_presenter

app/views/about/show.html.haml

@@ -20,7 +20,7 @@
     = image_tag asset_pack_path('logo.png')
     = Setting.site_title
 
-  %p= t('about.about_mastodon').html_safe
+  %p!= t('about.about_mastodon')
 
   .screenshot-with-signup
     .mascot= image_tag asset_pack_path('fluffy-elephant-friend.png')
@@ -32,7 +32,7 @@
         - if @instance_presenter.closed_registrations_message.blank?
           %p= t('about.closed_registrations')
         - else
-          = @instance_presenter.closed_registrations_message.html_safe
+          != @instance_presenter.closed_registrations_message
         .info
           = link_to t('auth.login'), new_user_session_path, class: 'webapp-btn'
           ·
@@ -74,7 +74,7 @@
 
   - unless @instance_presenter.site_description.blank?
     %h3= t('about.description_headline', domain: site_hostname)
-    %p= @instance_presenter.site_description.html_safe
+    %p!= @instance_presenter.site_description
 
   .actions
     .info