[FIX] web_editor: fix summernote text drop on firefox

Issue

    - Have firefox
    - Go to any chatter
    - Open full editor
    - Write some "test" words with line breaks
    - Select one of your "test" words
    - Drag & drop it somewhere else in the editor

    Welcome on test.com! (redirected)

Cause

    Summernote doesn't preventDefault on drop event, so firefox
    think we want to go to another URL.

Solution

    Add the preventDefault manually.

    This reveals another issue which is solved by importing
    this PR's code summernote/summernote#3327
    (with adaptation for our dinosaurus version)

OPW-2158112

X-original-commit: e476456