fix: request context processor added

before this, if you ran migrate, this would show up:
WARNINGS: 'django.template.context_processors.request' must be enabled in DjangoTemplates

close openedx#335

workbench/settings.py

@@ -43,6 +43,7 @@
                 'django.template.context_processors.debug',
                 'django.template.context_processors.i18n',
                 'django.template.context_processors.media',
+                'django.template.context_processors.request',
                 'django.template.context_processors.static',
                 'django.template.context_processors.tz',
                 'django.contrib.messages.context_processors.messages',