[FIX] web_editor: Evoid the risk of deleting the summernote library

For iframes, we need to inject summernote because there are references
to "document" in it. When loading the iframe, if it is canceled, there
is a risk that the library is erased and that it breaks the field html.
We must also slightly modify the library to prevent it from making
changes to the library of the main "window".