ensure plugin symlinks before compiling js

Change-Id: I7e52ee10ae3e6d4e666452a7a53e5459dfad43f4
Reviewed-on: https://gerrit.instructure.com/129032
Reviewed-by: Cody Cutrer <cody@instructure.com>
Reviewed-by: Ryan Shaw <ryan@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>
QA-Review: James Williams  <jamesw@instructure.com>
Tested-by: James Williams  <jamesw@instructure.com>

lib/tasks/js.rake

@@ -36,6 +36,7 @@ namespace :js do
 
   desc "Build webpack js"
   task :webpack do
+    require 'config/initializers/plugin_symlinks'
     if ENV['RAILS_ENV'] == 'production' || ENV['USE_OPTIMIZED_JS'] == 'true' || ENV['USE_OPTIMIZED_JS'] == 'True'
       puts "--> Building PRODUCTION webpack bundles"
       system "yarn run webpack-production"