Nested lists are inserted using invalid html when using editor buttons

Since Anki has its own buttons for creating nested lists (via the insert list and indent buttons), introduced in version 2.1.45 I believe, this bug from [glutanimate/mini-format-pack](https://github.com/glutanimate/mini-format-pack/issues/26) equally applies here. It creates problems when trying to export Anki notes and use them with tools like [anki-editor](https://github.com/louietan/anki-editor) and [org-anki](https://github.com/eyeinsky/org-anki). I found [one mention](https://forums.ankiweb.net/t/bug-anki-displaying-list-incorrectly/5075/5) of this issue in the forums but no solution (other than to not use the buttons).