the TOC is not scrollable in the online nvim doc v2

[haolian9]

to reproduce:

• open this page in a browser
• open the "developer tools" and resize it until the TOC is longer than the window (this helps to emulate how the page is showed in laptops)

i found the following css changes can help this situation.

.toc {
    height: 100%;
    overflow: auto;
}

[justinmk]

Thanks for suggesting that fix! The css class is here if you want to send a PR: https://github.com/neovim/neovim/blob/06f4edc864479fb121d514ec1e7253dba85b740d/scripts/gen_help_html.lua#L752