Add sdg help page

In this page we will render a list of clickable Goals icons that will show their
targets and related local targets

Co-authored-by: Senen <senenrodero@gmail.com>

app/controllers/sdg/goals_controller.rb

@@ -11,4 +11,8 @@ class SDG::GoalsController < ApplicationController
 
   def show
   end
+
+  def help
+    @goals = @goals.order(:code)
+  end
 end