Move linters to a Rake task

This allow running all linters in a single pass.

Rakefile

@@ -5,6 +5,14 @@ require File.expand_path('config/application', __dir__)
 
 Rails.application.load_tasks
 
+task :lint do
+  sh "bundle exec rubocop"
+  sh "bundle exec haml-lint app/views/"
+  sh "bundle exec scss-lint app/assets/stylesheets/"
+  sh "bundle exec brakeman --no-pager"
+  sh "yarn lint:js"
+end
+
 task :deploy do
   domains = %w(37.187.249.111 149.202.72.152 149.202.198.6)
   domains.each do |domain|