Mootools issue in com_content

[PierreCorell]

popup windows of jodit are not closeable because of mootools

details to reproduce:

• Joomla! 3.8.13
• go into Backend
• edit an article (com_content) with Jodit editor
• open any jodit popup, for eg. browse images
• try to close it
• nothing happens (console error)

error details
console error:
jodit.min.js?v=3.1.11:10 Uncaught TypeError: Cannot read property 'toggle' of undefined

it is a conflict with the mootools library, which is still in the Joomla! core (Joomla! 4 will remove mootools )
confirmed by temporarilly renamed mootools files (media/system/js/mootools-*.js)