Have Workbench warn the user to deactivate derivative-generating Contexts if it thinks the user is adding media that might trigger those derivatives

[mjordan]

Warnings in the docs here and here tell the user to temporarily disable Contexts that generate derivatives. In both cases, Workbench can use configuration settings to trigger a warning to the user. For example, if the user has configured Workbench to add thumbnails via additional_files, Workbench could tell them to disable the relevant Context. Similarly, if paged_content_additional_page_media is present in the config, they could get a similar warning.