NOTE: The deprecation patch can be merged once T287410 is resolved. This completes the technical goal of T282045
In T89981 we split out the `legacy` feature (ResourceLoaderSkinModule) into multiple parts.
In T287410 we disables its usage across all skins.
As part of the change we should also deprecate the `content` feature and `content-thumbnails` feature which currently act as aliases for other modules.
# TODO
* [ ] skins that use the `legacy` option should send a deprecation warning to the JavaScript console. This will need to be sent inside ResourceLoaderSkinModule
* [ ] skins that use the `legacy` option should send a deprecation warning to the JavaScript console. This will need to be sent inside ResourceLoaderSkinModule
* [ ] Update `docs/uidesign/design.html` to include the appropriate styles once legacy is removed.