[2.0.0-beta1] Component selector: use SDC's thumbnailPath?

Added related issue.

Thanks Mathieu.

This related issue will be useful if we store the thumbnails file outside the component directory and/or we name it something different from "thumbnail.png".

We can still process this issue without waiting the related issue to be done.

postponed to beta3 and let's investigate a popup window like in the "paragraphs" module,
Fieldwidget "paragraph", with the add mode option "Modal form"

This kind of UI features is now in the scope of https://www.drupal.org/project/display_builder →