Table of contents not functional in reader view

[Nanogamer7]

When switching to reader view, the "table of contents" title stays, with the "collapse/expand" arrow still present but it's not functional

Collapsed table of contents

Expanded table of contents_

Tested in Firefox Nightly 85.0a1

[DrMagPie]

this seams to be the case on most browsers.
and issue seams to be in html markup used for ToC.... reader view just ignores content of it...

We can try to handle ToC differently, but then we will need to create some fancy mechanism to collapse it.